Twelve units is where the feasibility math changes character and most builders underestimate how much it changes.

The assumption doing the most work in the condo exit scenario is the absorption rate, and you named it, but the compounding effect is worth pressing further. Most proformas model absorption as linear, say four units a month in your example, but condo sellouts rarely move that way. You get a burst at launch, a dead middle, and a tail that drags. If your interest reserve is sized for 18 months of carry post-CO and you hit month 14 with three units left, you are negotiating a reserve extension with a lender who now holds a partially-sold project as collateral. That conversation is harder than the original loan.

The bulk sale path has a different problem. The cap rate a buyer applies is not just today's cost of capital, it is today's cost of capital plus a liquidity premium for a newly constructed building with no operating history. On a twelve-unit asset, that premium is real and often 25 to 75 basis points above a stabilized comparable, depending on the market. That spread can erase the per-unit hard cost savings you built the thesis around.

The presale threshold constraint you raised is the one I would focus on hardest before anything else. Thirty to fifty percent under contract before the first draw means you are running a sales program before you have a product, which requires a marketing budget, a model unit strategy or renderings, and a sales timeline that your interest reserve may not have been sized to cover. Confirm with your lender in writing exactly how they define "under contract" for that threshold, because some lenders require hard deposits and others accept reservation agreements, and those are very different levels of buyer commitment.

The risk you did not mention is condominium conversion approval. In many jurisdictions, a twelve-unit building requires a condo map filing, HOA formation, and disclosure package before you can close individual units. The timeline on that process varies significantly and can compress your post-CO window in ways that interact badly with a tight interest reserve.

What does your current interest reserve cover in months, and is that measured from first draw or from projected CO?

The presale threshold is often misread as a lender preference when it is actually a condition precedent to the first draw, meaning you can close the construction loan and still not see a dollar until you hit it.

Absorption rate is where I would push back on the 18-month sellout framing: the number that matters is how many months past CO you are still carrying construction debt, because most condo conversions require the construction loan to be retired or recast before individual unit closings can proceed cleanly, and that sequencing adds cost the proforma treats as zero.

What is the current months-of-supply figure for comparable condos in your target submarket, and is that supply attached or detached, because those two pools do not compete the way most developers assume?

@reba_finch09 here. The piece worth adding is what happens when the condo exit and the bulk rental sale both get stress-tested at the same time, because a twelve-unit project almost always starts in one market cycle and lands at CO in a different one. A builder who structures the construction loan for a condo sellout typically cannot pivot to a bulk rental sale without a refinance event, and that refinance event requires an appraiser to underwrite stabilized rents at whatever cap rate buyers are applying at that moment, not the cap rate that made the deal look good eighteen months earlier. The mechanism that tightens this further is the construction lender's standard restriction on converting to a rental hold without full payoff or lender consent, so the optionality most builders assume they have does not survive the loan documents. Running a parallel proforma at origination, one for the condo sellout and one for a bulk sale at a cap rate 50 to 75 basis points wider than today's market, is the haircut that tells you whether the deal is genuinely feasible or only feasible if everything goes right. What does the construction loan term look like on the deal you're modeling, and does it include an extension option if the sellout runs long?

The thing I have never seen work is building spec condos in a submarket without a firm read on the HOA absorption problem. Everybody models the sellout, almost nobody models what happens when you are the declarant trying to hand off control of a six-month-old HOA to a buyer pool that includes a mix of owner-occupants and small investors, and the lender on unit seven wants two years of HOA financials that do not exist yet. I watched a guy in Frisco do exactly this on a ten-unit townhome project in 2021, sold six units clean, then stalled on four because two buyers could not get conventional financing approved against an HOA reserve study that showed 14 percent funded. He ended up dropping price 8 percent on the last three just to clear the loan.

What actually changes at twelve units versus one or two is that the project starts requiring infrastructure you cannot cut when margins compress. Dedicated construction superintendent, third-party inspections your lender mandates, a geotechnical report that costs real money before you pull the first permit. On my side of it, as a GC, I can tell you the shared foundation savings are real but they top out around unit eight, and from there the mechanical coordination costs start climbing because you are running shared HVAC infrastructure that requires engineering sign-off on every revision. The 15 to 20 percent hard cost savings the post mentions is achievable in ground-up wood frame garden style, less so in anything attached over a podium. What's your submarket, and are you talking for-sale or hold?

The misconception I'd push back on is that the 15 to 20 percent per-unit hard cost savings is a given. That figure assumes a mid-density wood-frame building on a site with clean geotech, standard utilities, and no unusual setback or fire separation requirements. Add a type III-A classification, a sprinkler riser, and an elevator shaft for ADA compliance, and the shared-structure advantage narrows to nearly nothing by the time you pull the final permit set.

What the original post models well but does not price is the soft cost structure at this scale. A twelve-unit building crosses the threshold where many jurisdictions require a licensed architect of record, a structural engineer with stamped drawings, and a separate MEP engineer, and those three fees together can run 8 to 12 percent of hard costs on a project this size, which is a higher percentage than on a 40-unit where you amortize the same fee structures over more doors.

The absorption rate point is the right one to close on, and the number worth adding is what happens to your construction loan extension clause if you miss the presale threshold at month 18 and the lender's preferred exit is a discounted bulk sale rather than a workout. Most builders read the extension option as cheap insurance and do not read the condition precedent language carefully enough to see that the extension is at the lender's discretion, not the borrower's right.

What does the jurisdiction's condo map act or subdivision ordinance look like for a building this size, because that filing timeline often adds four to six months that no proforma I have ever stress-tested accounts for correctly?

@reba_finch09 wrote "every one of those months after stabilization is carry the proforma probably did not model carefully enough" and that line is doing real work in this thread.

I am not building twelve units, I am under contract on a duplex in Spokane, so my numbers are a different scale entirely, but I have been running the absorption math obsessively because the mechanic is the same whether it is two units or twelve. What I keep landing on is that most proformas I have seen shared in forums like this one treat the sellout period as a fixed assumption rather than a range, and the difference between a three-month sellout and a nine-month sellout on a twelve-unit condo project at, say, a 10 percent construction loan is not a rounding error. On a $3M draw balance that is somewhere around $22,500 a month in interest alone, so a six-month slip in absorption is $135,000 that probably is not in the deal when it was underwritten.

The question I cannot answer from where I sit, and genuinely want to understand before I ever try something at this scale, is how builders are sizing the interest reserve upfront when the lender and the builder both have incentive to understate carry time to make the deal close. Who is actually stress-testing the absorption assumption, or does that just get negotiated away?

The presale threshold is not a sales-momentum tool the lender imposes to protect the project's reputation, it is a credit trigger that determines when the loan funds, and builders who treat it as a formality to get through rather than a forecast to stress-test end up with a draw schedule that stalls in month three.

What the original post does not fully price is the interaction between absorption rate and the construction loan's extension provisions. Most 18-to-24-month construction loans on a twelve-unit project include one or two six-month extensions, but those extensions carry a fee, usually 25 to 50 basis points of the outstanding balance, and they reset the interest reserve calculation at whatever rate the extension rider specifies, which may be higher than the original note rate if the index has moved. So a project that modeled a clean 22-month build-and-sell, hits a four-month permitting delay, and then enters a market where buyers are waiting on a rate decision can find itself burning through two extension fees and recalculating the reserve on a balance that has not yet started to pay down. That sequence alone can add 3 to 5 points to total project cost on a mid-market twelve-unit building, and it rarely appears as a named line item in a first-pass proforma. What absorption rate are you working from, and does your interest reserve model the extension scenario explicitly or does it assume a single clean loan term?

What cap rate does your bulk buyer actually quote you in that market right now?

Four months into my BRRRR prep and I've been stress-testing exactly this kind of proforma, so the absorption rate piece hits different when you're actually running numbers on real submarkets. The line that caught me was "every one of those months after stabilization is carry the proforma probably did not model carefully enough," because in my experience even careful builders low-ball the soft cost tail, specifically property taxes, insurance, utilities on unsold units, and the construction loan extension fee if you blow past the original maturity date, which on a 12-unit condo sellout in a slow market is basically guaranteed. I've seen extension fees run 0.5 to 1 percent of the loan balance per extension, and nobody's got that on line 47 of their proforma. What's the construction lender's extension policy on the deals you're actually seeing, and is that fee baked into the interest reserve or is it a surprise at month 20?

Absorption rate and bulk sale cap rate are both covered above, so the piece worth adding is what happens between CO and stabilization when the two exits are not cleanly separated. Some builders condo the units but cannot hit the presale threshold before the construction loan matures, and the lender converts or calls the note before enough units close. Say you have a 12-unit building with a 24-month construction loan, a 40 percent presale requirement, and a submarket moving 3 units a month pre-CO. You may enter the sales period with 4 units under contract, which satisfies the threshold, but if 2 of those buyers walk during construction, you are back below the trigger and the lender has options you do not want them exercising. The presale threshold is a floor, not a guarantee of loan compliance through the full term, and the extension fees and default provisions in the construction loan documents are where that risk actually lives. What does your construction loan term look like relative to your projected sellout timeline, and have you modeled what happens if absorption runs at half the rate you are assuming?

@reba_finch09 wrote "the interest reserve on a construction loan that runs 18 to 24 months is a real line item" and yes, but the number people get wrong is what happens when the draw schedule slips and the reserve runs dry before CO.

My Phoenix LP experience was a 96-unit deal, different scale, but the same mechanical problem showed up. The interest reserve was sized to the original 20-month schedule. Project ran 27 months because of a subcontractor default on mechanical in month 14. The sponsor had to come back to LPs for a reserve extension contribution, about $4,200 per unit in additional capital calls, and two LPs who couldn't fund got diluted down. On a twelve-unit project you're doing yourself, that same dynamic hits your personal cash rather than a capital stack, which is actually cleaner in some ways, but it means you need to know going in what the lender's policy is on reserve modifications. Some will allow a funded extension at closing if you escrow extra at origination. Most won't offer that unless you ask specifically in the first term sheet conversation, before the letter of intent is signed. After that point the lender has no incentive to give you favorable terms on a modification you might never need. What's your projected construction timeline and how much cushion beyond that is the lender actually reserving?

Absorption rate and cap rate are the two variables in the post, but the one that tends to surprise builders is what happens between certificate of occupancy and the last closing when the construction loan does not convert. Most construction lenders will call the loan at maturity regardless of how many units have closed, so if absorption runs slow and the loan term ends at month 18, the builder is refinancing an unsold inventory into a bridge or mini-perm at whatever rate exists that week. Confirm with your lender in writing whether partial releases are available as individual units close, because that mechanism is what lets the loan balance shrink in pace with the sellout rather than sitting full until the end.

What does your current lender quote look like on the release premium per unit?

Twelve-unit condo projects in a mid-tier submarket, I've watched three of them stumble on something the proforma never captures cleanly: the homeowner association documents have to be recorded before you can close a single unit, and in most states the HOA budget has to be funded at a level the lender reviewing the buyer's mortgage will accept under agency guidelines. Fannie has a rule that the HOA has to be investor-concentration-compliant and adequately insured before they'll buy the loan. If you're building in a submarket where the condo insurance market is thin or expensive, that insurance line alone can blow the HOA budget to a number that makes the monthly dues unattractive to buyers who were already rate-sensitive.

The reason that detail bites is timing. You don't find out the insurance quote is $800 a month per unit instead of $400 until you're close to CO, the presale contracts were written with a dues estimate in the disclosures, and now you have buyers who can argue material change and walk. That's not a financing problem, it's not an absorption problem, it's not a rate problem, it's a $400 difference in a line item that nobody priced in 2021 when the project was underwritten. I'm working through seller financing on a 3-bed in Maplewood right now and the due diligence on something this simple is already making my head hurt, so I have a lot of respect for anyone running twelve units. What state are you building in, because the HOA formation rules vary more than people expect.

The risk I would add is on the construction loan structure itself: most twelve-unit deals get underwritten on an "as-complete" appraisal, and if that appraisal comes in short of the budget at commitment, the lender closes the gap by reducing proceeds, which means the developer funds the difference out of pocket before the first shovel moves. That shortfall does not show up in a proforma built around a contractor bid.

What does your current "as-complete" appraisal show relative to total project cost, and has the lender given you a loan-to-cost ceiling in writing?

Absorption rate is the number I would pull first, and it is hyperlocal enough that county data is almost useless. You want MLS solds by zip for the last 90 days on units under 1,500 square feet, specifically. I ran numbers on a 10-unit project in Burleson in 2023 and the county absorption looked fine until I filtered by product type and realized there were maybe 2 comps in 6 months.

What is your construction timeline assuming, and is that 18 to 24 month carry baked into the interest reserve or is it a stretch scenario?

Absorption rate in West Roxbury right now is slow enough that I keep backing out of condo projects before I even finish the proforma. Four units a month is optimistic for a lot of Boston submarkets outside the Seaport corridor, and if you are building twelve units in a neighborhood where three comparable condos have been sitting for 90-plus days, that sellout math gets ugly fast.

What I have never resolved cleanly is how to model the interest reserve when you do not know if you are selling or holding until you see where rates land at CO. Does anyone actually get construction lenders to write flexibility on that exit decision into the term sheet, or is that a fantasy?

Eighteen months of post-CO carry on a twelve-unit condo project assumes buyers show up in a straight line, and they never do. The first four units move fast because you get the curious and the committed, then you hit a wall around unit seven or eight where the remaining buyers want to see that the building is actually occupied and managed before they close. That middle stall is where the interest reserve runs out and the builder starts funding carry from somewhere else. What does your construction lender actually say about reserve extensions, and have you modeled what that costs at current short rates?