Can I make my resident address/ live/get mail) for the basement

[Joel Washington]

I was wondering could I make the basement a unit for myself. I know with 3 percent down fha loans, you have to live and make it your primary residence. Im looking at a  4 plex, but for the numbers I want I would have to live in the basement; while renting out all four units. Is this legal and can I get a mail box for the basement if it is?