A $400,000 triplex passes FHA’s rent test by $48. The duplex never takes it

A duplex and a triplex sit next to each other on the same listing page, and to FHA they are not the same kind of building. At three units a test switches on, and a building that would have sailed through as a duplex can fail it.

What changes when a building has three units?

Three things change at once, and only one of them is about the house.

The first is the test. HUD’s Handbook 4000.1, the rulebook FHA lenders follow, says the payment divided by the net self-sufficiency rental income “may not exceed 100 percent for three- to four-unit Properties.” That is its wording as of the August 12, 2026 revision. A one or two unit building is never measured that way.

The second is reserves. On a one or two unit property HUD asks for one month of the payment left in your accounts after closing. On three or four units it asks for three.

The third is how much FHA will lend at all. The limits climb with the unit count, so a fourplex can carry roughly twice the loan a single house can in the same county.

What does not change is occupancy. On any of these, at least one borrower “must occupy the Property within 60 Days” of signing the security instrument and intend to continue occupancy for at least one year. FHA is a loan for the building you live in, whether it has one door or four.

How does the self-sufficiency test work?

HUD defines net self-sufficiency rental income as the rent the building produces over and above the principal, interest, taxes and insurance. The calculation runs in two steps.

Start with “the Appraiser’s estimate of fair market rent from all units, including the unit the Borrower chooses for occupancy.” Your own unit counts, at market rent, even though you will not be writing yourself a check. Then subtract “the greater of the Appraiser’s estimate for vacancies and maintenance, or 25 percent of the fair market rent.” At least a quarter always comes off.

Set the result against the monthly payment. If the payment is the larger number, the building fails, and no amount of your own income makes up the difference. The FHA self-sufficiency post walks one fourplex through the arithmetic a step at a time.

The same $400,000 building, three ways

Take one price and change only the number of doors. A $400,000 building, bought with FHA’s minimum 3.5% down ($14,000) on a 30-year loan at an assumed 6.5%, with the example’s property taxes at $5,130 a year and insurance at $2,886.

The loan works out the same in all three cases. FHA’s maximum is 96.5% of the price, which is a $386,000 base loan, and HUD charges an upfront premium of 1.75% of that which can be added to the balance, bringing the loan to $392,755. With less than 5% down on a loan this size the yearly premium is 0.55% as of October 2026, charged on the $386,000, which is about $177 a month at the start. Principal and interest come to $2,482, so the whole payment is $3,327 whichever way the building is divided.

What changes is the rent. More units at the same price usually means smaller units and more rent in total.

These are example figures, not a quote.

Read the columns in order and the rule shows its teeth. The duplex misses by $477 a month, and it does not matter at all, because FHA never runs the test on two units. The triplex clears it by $48, which is a ratio of 98.6%. The fourplex clears it by $498, a ratio of 87.0%.

The triplex is the one to watch. At $1,479 a unit it passes with 35 cents to spare. At $1,478 it fails. One appraiser’s rent estimate $22 a unit below the seller’s rent roll is the whole margin.

How much do you put down, and hold back?

The down payment is the easy part: HUD sets the minimum required investment at “at least 3.5 percent of the Adjusted Value,” the lower of the price and the appraisal. On $400,000 that is $14,000 at any unit count.

Reserves are where the unit count bites again. One month of this payment is $3,327, which is what a one or two unit building needs. Three months is $9,982, which is what the triplex and the fourplex need. It has to be your own money: reserves do not include “borrowed funds from any source” or equity in another property.

So the duplex asks for about $17,327 before closing costs, and the triplex asks for about $23,982 to buy exactly the same real estate. The extra $6,655 buys you a third rent check.

How much can FHA lend on each one?

FHA’s limits are set by county and rise with the unit count. For loans in 2026 the floor, which applies in low-cost areas, runs like this.

In the highest-cost counties the ceilings are far higher: $1,249,125 on one unit and $2,402,625 on four. Both sets come from HUD’s letter setting the 2026 limits, published December 11, 2025, and your own county sits somewhere between the two.

If you rent out every unit instead of living in one, FHA is off the table and a conventional loan caps out lower: as of October 2026 Freddie Mac allows 85% of the price on a one-unit rental and 75% on two to four units. That turns $14,000 into $100,000 on this building. Living there is what makes the small down payment possible, and what living there is actually like is worth reading before you sign for it.

Which one should you run first?

Price the triplex and the fourplex on the appraiser’s rents, not the seller’s. Put the building into the FHA self-sufficiency calculator with 75% of what comparable units nearby actually lease for, your own unit included, and set it against a lender’s estimate of the full payment including the monthly premium.

If it only passes at the rent roll you were handed, that is the number to verify before anything else. For a duplex there is no test to pass, so the question goes back to the rents themselves: how to analyze a duplex covers that, and how to analyze a small multifamily property covers the rest of the building.