Is a house with an ADU, or a duplex, a home or a rental?
A home. Mortgage rules treat a property with up to four units as a residence when the buyer will live in one of them. A home loan can buy it, and the other units are a rental you run.
WHAT MOST PEOPLE ARE NEVER TOLD
The federal rulebook for FHA loans puts a duplex in the same class as a house. It defines a two-unit building as a "Single Family residential Property with two individual Dwelling Units."
The line is who lives there. Move into one unit and the duplex can get a home loan. Buy it without moving in and lenders class the same property as an investment, with different rules and pricing.
Two of the main rulebooks for home loans, Fannie Mae's guide and FHA's handbook, stop at four units. A building with five is outside both. A house with one ADU is a one-unit home in the same rulebooks.
A duplex is marketed and priced as an investment, and agents who mostly sell houses rarely handle one. So the people who would live there never see it offered to them.
GOOD TO KNOW
Fannie Mae and FHA rules require you to move in within 60 days of closing and plan to stay at least a year. You are the landlord from day one, with leases, repairs and a tenant through the wall.
Yours is a little different. They all are.
Tell us what you are looking at and what you are trying to do. We answer with the numbers on your situation.
Free. No credit pull.
WHERE THIS COMES FROM
- Fannie Mae Selling Guide B2-1.1-01, Occupancy Types (11/04/2026)
- Fannie Mae Selling Guide B2-3-01, General Property Eligibility (09/03/2025)
- HUD Handbook 4000.1 (FHA), Occupancy Types, section II.A.1.b.iii (page 159, revised 8/12/2026)
- HUD Handbook 4000.1 (FHA), Property Types, section II.A.1.b.iv(B) (pages 169 to 170, revised 8/12/2026)
- Fannie Mae Selling Guide B2-3-04, Special Property Eligibility Considerations: Accessory Dwelling Units (November 4, 2026)
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.