Here's some snippets from the HUD handbook on the subject:
"A principal residence is a property that will be occupied by the borrower for the majority of the calendar year"
And
"FHA security instruments require a borrower to establish bona fide occupancy in a home as the borrower's principal residence within 60 days of signing the security instrument, with continued occupancy for at least one year."
Thanks. for a house hack on a duplex for an example where Im renting one unit, after 183 days I can begin rent out my unit?
I don't think the FHA is going to be checking up on you...