Classification of duplex – single or multi-family

On a few occasions looking on,, or other government/bank websites properties have been loosely defined as a single family. Do these institutions consider any residential property with 1 to 4 units a single family and anything else a multi-family?
If this is true, what strategies do you use to filter through listings if you are looking for a 2+ unit property?
Any advice would be great!

While the government websites you reviewed might appear to “loosely” define things government regulatory agencies and hence the banks/thrifts they oversee are very specific in how they define their loan categories.

Single Family = 1-4 residential units
Multi-Family = 5+ residential units
Commercial RE = nonresidential income producing

most banks etc will consider under 4 units a single family

1 unit - Single family home
(FHA financing available)

2 to 4 units- Multifamily Residential
(FHA limits owner occupied financing to 4 units)

5 units and up- Commercial residential
(No FHA owner occupied financing)