Do all lenders use 75% of the rent?

No. 75% is Fannie Mae's rule for loans sold to it. Other loan programs and lenders can use a different percentage, so ask yours.

Does the rent from my own unit count?

No. You live in it, so it produces no rent.

Do I need an appraisal with a rent schedule?

Under Fannie Mae's guide, yes: the lender needs Form 1007 or Form 1025 to support the gross monthly rent.

How Lenders Count Rent on a Duplex You Live In

Under Fannie Mae's guide, a lender counts 75% of the gross monthly rent and then subtracts the full housing payment on the property. The 25% haircut covers vacancy and upkeep. Other lenders and loan programs may count rent differently, so ask yours which rule applies.

The 75% rule in plain words

Fannie Mae's Selling Guide (B3-3.8-02) says that on a purchase, the lender takes gross monthly rent and multiplies it by 0.75 to get net rental income. It then subtracts the property's monthly housing payment: principal, interest, taxes, insurance and any association dues (PITIA). A positive result counts as income. A negative result counts against you as a monthly obligation.

For the rent figure, the guide requires an appraiser's rent schedule (Form 1007) or a small residential income appraisal (Form 1025), plus a signed lease if one transfers to you. The rent the lender uses is therefore the appraiser's market rent and the lease, not your guess.

A worked example

Example a made-up fourplex. You live in one unit and the other three rent for $1,200, $1,250 and $1,300 a month, so gross rent from the rented units is $3,750. Seventy-five percent is $2,812.50. The whole building's payment (PITIA) is $3,400 a month.

Example $2,812.50 less $3,400 is a negative $587.50. The lender counts that $587.50 as a monthly obligation next to your other debts, so your own income has to cover the gap.

Notice what happened. Rent of $3,750 against a payment of $3,400 looks like it covers the building, yet it came up short after the 25% cut. That is the difference between how lenders measure and how owners experience the building.

What about the unit you live in?

The unit you occupy produces no rent, so it adds nothing to the 75% figure. Fannie Mae also lists a property-management experience condition for counting rental income on a two-to-four-unit main home, so read that part of the guide or ask your loan officer. How a given lender nets the income against the payment can differ from the example above, which is another reason to ask for the worksheet it will use.

How that feeds the debt-to-income ratio

Your debt-to-income ratio compares monthly debts with gross monthly income (the CFPB explains the ratio). A positive net rent is added to income. A negative one is added to debts. Either way the rent changes the ratio.

What to do before you make an offer

Ask the loan officer which rental income rule applies to your loan.
Ask for the appraiser's rent schedule early, so you know what the lender will count.
Run the 75% math yourself on the seller's rent roll. See what a rent roll should show.
Keep the real numbers in a separate sheet: your true cost of living there is a different question, answered in the real monthly cost of a house hack.

Why lenders cut the rent at all

A lender does not assume every unit is rented every month at the full rent, and it knows a landlord pays for repairs, turnover and management time. Counting 75% of gross rent is a simple way to allow for those costs without asking for a full operating budget. Real vacancy and repairs on your building may run lower or higher, which is why the lender's number and your own budget should sit side by side. Do your own version using the unit-by-unit rent and costs, then compare it with what the lender will count. If your own number is lower than the lender's, trust yours when deciding what you can afford. Keep in mind too that the appraiser's market rent and the lease can differ from what the seller advertises, and the lender uses the documents, not the listing.

How DoorKeeping fits

DoorKeeping does not make loans or predict what a lender will count. After you buy, it keeps the rent roll and the books for the building, so the next lender or your tax preparer gets a rent roll and a year of statements without a weekend of spreadsheet work. It costs $2 per unit per month.

Sources

Fannie Mae Selling Guide, B3-3.8-02 Rental Income from the Subject Property (75% of gross rent, Form 1007 or 1025), read Oct 31, 2026
Fannie Mae Selling Guide, B2-1.1-01 Occupancy Types, read Oct 31, 2026
CFPB, What is a debt-to-income ratio?, read Oct 31, 2026

Questions

Do all lenders use 75% of the rent?: No. 75% is Fannie Mae's rule for loans sold to it. Other loan programs and lenders can use a different percentage, so ask yours.
Does the rent from my own unit count?: No. You live in it, so it produces no rent.
Do I need an appraisal with a rent schedule?: Under Fannie Mae's guide, yes: the lender needs Form 1007 or Form 1025 to support the gross monthly rent.