Is renting out part of the home you own a new idea?
No, it is an old one. In 1950 almost one in five American homes was in a two-to-four unit building, according to the Census Bureau. The loan rules for an owner who lives in one unit are on the books today.
WHAT MOST PEOPLE ARE NEVER TOLD
The FHA's handbook files any home with one to four units under "Single Family" mortgages. To the agency that insures the loan, a fourplex you live in is in the same rulebook as a house.
Boston calls them triple-deckers. Chicago calls them two-flats. Often the owner lived on one floor and rented out the others.
The Census Bureau puts their high point, as a share of all homes, at 1950. By 2000 they were fewer than one in ten homes. Few new ones are built.
When you live in one unit, the FHA and Fannie Mae let a lender count part of the rent from the others as your income, with conditions. The part counted is usually 75 percent.
GOOD TO KNOW
After 2008 Fannie Mae and Freddie Mac tightened their requirements on these homes, and their share of home lending fell by about half. The rules have eased since and can tighten again, so ask a lender for today's, and plan for repairs: these homes are older on average than single houses.
Yours is a little different. They all are.
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WHERE THIS COMES FROM
- U.S. Census Bureau, Historical Census of Housing Tables: Units in Structure
- HUD Handbook 4000.1, FHA Single Family Housing Policy Handbook (revised August 12, 2026): section II.A, page 126 (one to four units); pages 240 to 241 (rental income)
- Fannie Mae Selling Guide B3-3.8-02, Rental Income from the Subject Property (09/02/2026)
- U.S. Census Bureau, New Residential Construction: Housing Units Started, annual table by units in structure
- Urban Institute, Default and Loss Experience for Two- to Four-Unit Properties (Goodman and Zhu, 2016)
Researched and written by Series Homes. Checked against its sources on . Lending rules change. This page is general information, not a loan offer or legal or tax advice.