Calculating Rental Income for House Hacking Properties

Estimate the rent for each unit or room you won't live in from recent leases on similar units nearby, then check it against the appraiser's market rent, because lenders rely on the appraiser's figure. FHA, Fannie Mae, and VA lenders generally count 75% of that rent toward qualifying, and VA adds landlord-experience and reserve conditions. A 3- or 4-unit property bought with an FHA loan must also pass a self-sufficiency test: the market rent for every unit, including yours, after deducting the greater of 25% or the appraiser's vacancy and maintenance allowance, has to cover the full mortgage payment. Then run a second, stricter test for yourself: whether the rent covers operating costs and reserves, both while you live there and after you move out.

This page covers the numbers. For how house hacking works overall, start with what house hacking is and how it works.

How do you estimate the rent for the other units or rooms?

1. Pull 3 to 6 comparable rentals. Match bedrooms, bathrooms, size, condition, and parking, within the same neighborhood. Leased rents beat asking rents, because listings that sit unrented show what the market rejected. A local property manager or agent can often tell you what similar units actually leased for.
2. Adjust for differences. Subtract for features the comps have and your unit lacks, such as in-unit laundry or central air, and add for what your unit has that they don't. Note who pays which utilities, since a comp with water included is not the same rent as yours.
3. Read the existing leases. If tenants are staying, ask the seller for the leases and proof the rent is being paid. A below-market lease limits your income until it ends, and before assuming the rent resets to market afterward, check whether a state or local rent cap applies.
4. Expect the appraiser's estimate to carry the most weight. For a 2-4 unit purchase, the lender orders an appraisal that includes the appraiser's estimate of market rent for each unit. FHA uses the lower of that estimate or the lease. Fannie Mae requires the appraisal's rent schedule to support a lease amount; when market rents don't, the lender either documents in writing why the lease rent is stable or uses the lower figure.
5. Subtract a vacancy allowance for your own budget. The national rental vacancy rate was 7.3% in the second quarter of 2026, according to the Census Bureau. Use a local figure if a property manager can give you one, since vacancy varies by market and by unit type.

For a room rental inside your own unit, comps come from room listings in the same area, and the rent depends heavily on whether the room has its own bathroom. Renting spare rooms covers how lenders and leases treat rooms.

How much of the rent do lenders count?

Debt-to-income ratio (DTI) is your monthly debt payments, including the new mortgage, divided by your gross monthly income. The 25% that lenders leave out is their allowance for vacancy and upkeep, and it is not a budget you can rely on yourself. Room rentals are harder to count: FHA counts boarder income only from a boarder who already lives with you under a written agreement and has paid you for at least 9 of the last 12 months. The FHA lender divides documented receipts over the last 12 months by 12, including unpaid months, and uses the lesser of that average or the current written-agreement rent, capped at 30% of qualifying income. Fannie Mae generally doesn't count boarder income except under its HomeReady program for lower-income buyers, which counts it on a one-unit home only when the boarder has lived with you for the past 12 months and paid you rent for at least 9 of them. HomeReady also divides documented receipts over the last 12 months by 12, including unpaid months, and caps the amount at 30% of qualifying income. Financing your first house hack compares the loans themselves, and house hacking with a VA loan covers the VA side.

Worked example: the FHA self-sufficiency test on a triplex

FHA's rule: take the appraiser's market rent for all units, including the one you will live in. Subtract the larger of the appraiser's vacancy and maintenance estimate or 25%. The full monthly mortgage payment (principal, interest, taxes, insurance, and FHA mortgage insurance) divided by that net rent cannot exceed 100%.

Example triplex at $450,000 with 3.5% down ($15,750):

• Base loan: $434,250. FHA's upfront mortgage insurance of 1.75% ($7,599) is added, for a loan of $441,849.
• Principal and interest at 7.0% for 30 years: $2,940. The 7.0% is an assumption for this example; Freddie Mac's weekly survey average for a 30-year fixed loan was 7.32% on October 22, 2026, so use your own quote.
• FHA annual mortgage insurance at 0.55% of the base loan: $199.
• Property taxes $450 and hazard insurance $250.
• Total monthly payment: $3,839.

If the appraiser puts each unit at $1,500: $4,500 x 75% = $3,375. $3,839 / $3,375 = 114%. The property fails, and the loan can't close as structured.

If each unit appraises at $1,750 and the appraiser's vacancy and maintenance allowance is no more than 25%: $5,250 x 75% = $3,937.50. $3,839 / $3,937.50 = 97.5%. The property passes the self-sufficiency test under that assumption.

To find the rent you need before making an offer, divide the payment by 0.75 if the appraiser's vacancy and maintenance allowance is no more than 25%: $3,839 / 0.75 = $5,119 a month across all three units, or about $1,706 a unit. If the allowance exceeds 25%, divide the payment by the share of rent remaining after that allowance instead; the required rent will be higher. If comps don't support that, lower the price, put more down, or look at a duplex, where FHA doesn't apply this test.

For qualifying at $1,750 a unit, the lender adds 75% of the rent for the two units you won't live in ($3,500 x 75% = $2,625) to your gross income and counts the full $3,839 payment in your DTI. FHA also requires 3 months of payments ($11,517) in reserve after closing on a 3-4 unit property.

Does the rent cover the property's costs now and after you move out?

The lender's math doesn't include repairs, turnover, or utilities you pay. Your own budget should. Continuing the triplex at $1,750 a unit, with these assumed costs: vacancy 7% of rent collected, repairs and replacements 10% of rent, and $150 a month for owner-paid water, sewer, and trash.

While you live there, $1,084 a month is your effective housing cost. Compare it with the rent for a similar unit nearby; house hacking vs traditional renting runs that comparison with buying and selling costs included. After you move out, this property barely breaks even with a manager, so a rent shortfall or a major repair would come from your pocket. FHA requires at least one borrower to move in within 60 days of closing and intend to stay at least one year, so plan the move-out numbers before you buy.

Keep cash reserves beyond the lender's minimum. At $368 a month without a manager, a $10,000 roof or sewer line repair takes more than two years of cash flow to cover, and three units mean three sets of appliances and turnovers. How to calculate rental property cash flow shows how to set the repair and capital reserve rates for a specific building.