General property eligibility
Conventional does not mean “any house.” The property must be acceptable residential collateral under the selected agency's rules.
Fannie baseline
Fannie generally purchases first-lien mortgages secured by eligible one- to four-unit residential properties. A one-unit home with one qualifying ADU is still treated as a one-unit property.
Freddie baseline
Freddie requires the mortgaged premises to be primarily residential and acceptable in value, condition and marketability. Eligible forms can include detached, attached and semi-detached dwellings, PUDs, condos and certain co-ops.
Collateral matters independently from borrower approval
The lender must determine that the home is adequate collateral even when AUS approves the borrower. Appraisal or property-data findings can still make the transaction ineligible.
Official guide baseline
Fannie Mae Selling Guide · Freddie Mac Seller/Servicer Guide
Property eligibility, valuation method, appraisal findings, AUS messages and lender overlays all matter. The appraisal supports collateral eligibility; it does not replace underwriting.