What actually changes when a loan flips from residential to commercial at five units

Question

Consider a fourplex and a five unit on the same street, similar age, similar rents, where an agent calls the fourplex a residential loan and the five unit a whole different animal, commercial, with only a vague reference to how banks count doors. One to four units qualifies for standard residential mortgage financing: fixed rates, longer amortization, underwriting based heavily on the borrower's personal income and credit. Five units and up is treated as commercial regardless of how residential the building looks, which means underwriting shifts to the property's net operating income and debt service coverage, terms shorten, rates often run higher, and amortization periods compress. The building itself can matter at the margin, condition and unit mix affect underwriting on either side of the line, but the unit count determines which loan category applies in the first place.

Rena Guide · Accepted Answer

The line sits at four units and it's a lending definition rather than anything about the building. One to four units is residential for loan purposes, which means the loan is underwritten mostly on you, your income, your credit, your reserves, with the property's rent helping. Two units is a duplex, three a triplex, four a fourplex (some markets say quadplex, same thing). At five units and up the loan is commercial: underwritten on the property's income, usually a bigger down payment, a shorter term with a balloon, and personal guarantees.

So a fourplex can qualify for the same kind of low-down-payment owner-occupied program a single family house does, if you live in one unit. The five unit next door can't, even if it's physically identical with one extra bedroom walled off. Terms move around, so get the actual numbers in writing from a lender before you fall in love with a building.

One thing that catches people with your background especially: the count that matters is legal units. If a "fourplex" is really a triplex with an unpermitted basement apartment, the appraiser can count three, and that fourth rent may not be usable in underwriting at all. Whether the unit can be legalized depends on your local zoning and building code and how your state treats existing nonconforming use, so that's a question for the city and, if money is riding on it, a local land use attorney.

laurenkim53 · Answer

In markets where duplexes trade around $120k to $150k total, the appraisal usually causes more trouble than the loan box. A lender wants two comparable duplex sales inside the last year, and when those do not exist the appraiser reaches for single family comps and adjusts, which tends to bring the number in low.

renee_dubois · Answer

The count is the easy part. Worth adding is that four units under one roof usually means shared guts. One furnace or boiler, one water meter, one main line, one roof. So you get four rents and one very expensive failure point, and when that thing dies you do not get to fix a quarter of it. Ask for the age of the heating plant and the sewer line before you ask anything about rents.

karen_whitfield · Answer

@nicole_adeyemi given how you think about land, check whether the fourplex is a legal use or a grandfathered one. A grandfathered building that burns down can sometimes only be rebuilt to current zoning, which in a lot of towns means fewer units. That's an ordinance question and it varies town to town, but it changed how I read a couple of listings.

Rena Expert · Answer

Adding the mechanics under @laurenkim53's comp problem, because it's the part that sinks deals late. A 2-4 unit appraisal comes in on a different form than a single family, and it comes with a rent schedule where the appraiser states market rent per unit. Underwriting usually counts something like 75 percent of that market rent, not your actual leases, so a building rented $200 under market gets you less credit than you modeled, and a building rented above market gets you no extra credit.

On 3-4 unit purchases with certain owner-occupied programs there's an additional test where the property's net rental income has to cover the whole payment. That test uses the appraiser's market rents too. Duplexes are generally exempt from it. Get your lender to confirm in writing whether it applies to the file, because it's the single most common reason a fourplex pre-approval evaporates.

The five unit isn't automatically worse, it's priced differently. Commercial pricing keys off net income and a cap rate, so a five unit with weak rents can be cheap per door in a way a fourplex never is, since the fourplex is competing with owner-occupant buyers who pay on emotion and payment size. If you're a long hold buyer with cash, that spread is sometimes worth the commercial terms.

One risk nobody's raised: converting a legal fourplex to five units, say by finishing an accessory unit, can push you out of residential financing on the next refinance. People do that improvement and then discover the refi they were counting on doesn't exist at their old terms.

tashaford30 · Answer

The rent schedule point deserves restating plainly. The safest version is a fourplex where actual rents already sit at or near market, because the number the appraiser writes down then matches what the buyer will actually collect. Under-market rents get pitched as the whole opportunity, and sometimes they are, but whether an investor wants that gap at purchase or a year later is a fair question, and it is worth deciding before the offer goes in.

What actually changes when a loan flips from residential to commercial at five units

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