If you want a definition of the U. S. Census Bureau for multi-family, please see the link: https://www.economy.com/support/blog/buffet.aspx?did=8015A9FA-79EF-4EE6-BF79-C84EC932B331
The multi-family category includes all buildings containing at least two housing units which are adjacent vertically or horizontally. If built side-by-side, they (1) do not have a wall that extends from ground to roof, or (2) share a heating system, or (3) have interstructural public utilities such as water supply/sewage disposal.
This not to curt; instead, this is to help you to remember. The answer is in the title of the 1-4. Any more than 4 is considered multi family. A qudraplex or less (duplex, triplex) is considered single family.
Great question. In real estate, a 1-4 family home is considered single family. To keep it simple, any dwelling with 5 or more units is multifamily. If you have any additional questions, please feel free to reach out.
It would be constituted a more than one Living unit. Typically with separate electricity meters, water etc. Most importantly design, Each unit should have a kitchen, bath and areas to sleep. I won't say bedroom since efficiency style apartments would be disqualified. Basically, you need at least 2 separate units within the same structure that are designed to be lived in completely. 1 house with 20 rooms nor 1 lot with 4 separate de-tached houses would be considered multifamily. More than four you move away from the standard 1-4 Family Contract. A couple resources attached, thanks for asking the question it made me think about it.