Can I count rent from an ADU I haven't built yet, or does it have to already exist

I own a 1,100 square foot house on a corner lot, free of any loan, bought it years ago and lived in it since. Detached two-car garage at the back with alley access, 480 square feet, sound roof, slab in decent shape.

The zoning here allows a detached accessory dwelling unit on this lot size and my planner said a garage conversion is the common path. Contractor quoted 78 to 95k depending on whether we do a full bath or a three-quarter and whether the sewer lateral can be tapped where he thinks it can.

Similar studios in the neighborhood rent 1,050 to 1,200.

Here is what I'm confused about. I've read that as of March 2026 Fannie Mae lets buyers count projected ADU rent toward the income they qualify on, up to 30 percent. That sounds like exactly my situation except I'm not buying anything. I already own the house. I'd be borrowing to build the unit.

So does that policy help me at all, or is it only for someone purchasing a house that already has the ADU on it? My credit union loan officer said "probably a renovation product" and then had to take another call.

I have enough in savings to cover about 30k of the build and I'd need to finance the rest. I don't want to start drawings at 6k until I know whether the money exists.

Answer

2tashaford30PB2APRO7

Direct answer to what you asked. The Fannie Mae change taking full effect in March 2026 applies to purchase transactions on one-unit owner-occupied homes, letting a buyer count projected rent from an accessory dwelling unit toward qualifying income, capped at 30 percent of total qualifying income. It's for someone buying a house that has the unit, or has it appraised as part of the purchase. You already own yours, so that specific rule isn't your path.

Your path is a renovation or construction loan against the house you own. The mechanism there is different. The lender appraises the property based on what it will be worth once the ADU is finished, lends against that, and releases money in draws as the work is inspected. Whether any of them will count the future rent toward your income depends on the individual lender and product, and you should get that answer in writing before you commit to anything.

You have one big advantage that most people asking this don't. The house is paid off. That means a cash-out refinance is also on the table, and it might get you the 65k with less complexity than a draw-based renovation loan, at the cost of putting a mortgage on a house that currently has none. Run both. And do what @ledger said about the sewer lateral, because the difference between 78 and 95 is bigger than the difference between the two loan products.

4 replies

1jordan_ellis2ActivePRO6

The distinction that matters is purchase versus refinance. Everything I've read about the March policy describes it on purchase transactions for one-unit owner-occupied properties. You're a refinance or a renovation loan. Different rule set.

3hannah_west29 Get yours

Set the financing aside for a second and look at the build. 78 to 95k for 1,050 to 1,200 a month is a gross yield somewhere around 14 to 17 percent before anything. That's strong enough that the question of which loan product you use is secondary to whether the 95k number holds, and garage conversions with sewer uncertainty in them do not usually hold. Get the lateral scoped before the drawings, not after.

1dmitri_v6CapitalPRO6

Ask the credit union for the name of the product and the underwriting guide section, then read it yourself. Renovation loans that fund off the after-completion value exist, and some of them consider projected rent from the completed unit, but the terms differ a lot between lenders and between loan types. What you want in your hand is a written term sheet showing the appraisal basis and whether projected rent counts, before you pay for drawings.