Quoted:
A buddy is in the process of buying a house and moving to Az from out of state. He closes on the Az house in a few weeks, but will be going back and forth from out of state to the new house in Az for a few months before the move is permanent. Will he be able to buy a gun through an FFL as soon as he closes on the Az house and has an Az drivers license?
View Quote
That's generally how things work. On the 4473, as long as you have proof of residence (in the form of valid government issued photo ID with the usual junk on it), you're GTG to buy firearms using that ID and address.
If he's worried about it, and the dealer is intelligent--he could use property tax documents for the new house in conjunction with another valid ID to validate temporary two-state residence during the time of his move. Most dealers hate doing that, though, because they are terrible business people (IMO) and don't concern themselves with a situation that might be a 1-in-500 chance of happening.
Granted, this information is true as experienced through my business dealings in KY, so feel free to verify elsewhere if you wish.