It depends on the state.  In some states, you must live there for six months before you are legally a resident.  In others, you are instantly a resident when you move there.

Of course, for the purposes of buying a gun, by federal law, all that is required is INTENT to become a resident.  How an individual state or FFL handles that is something else, though.

A state ID is exactly the same as a state-issued driver's license for the purposes of buying a gun; you don't have to be able to drive a car to buy a gun.

If it were ever to come up in court, you would probably need to be renting/owning a place full-time in that state in order to be considered a resident.  Two-weeks per year in a time-share probably wouldn't be enough, but renting a room 12 months a year from someone should be fine.  You'd want a contract, etc.  And some states require you to LIVE in the state more than 6 months a year to be considered a resident, so that could be a problem.  You can be sure your employment records, bills, car registration, etc., would be checked.

Try posting some specific examples in the Legal forum.

-Troy

Having spent the last twenty years in the military I've moved around a bit. Typically within the first month or so I get a new state driver's license. I don't have to show any proof of anything - no military orders, bills with my name on them, nothing. I just show my old state ID and give them a new in state address.

California, Washington, Colorado and Illinois.

If it helps any, my father moved to PA and the gun shop's owner told him that he had to be living in state for 90 days before making a handgun purchase. He came from NYC. It also depends on the state that you came from, the FFL in PA told me that if my home state allows me to buy handguns without a permit, then they could also sell me a handgun even if I am not a resident of thier state. I am not sure if he was correct about that one, However for assault weapons, if you are allowed to buy them in your home state, you should be able to buy them in another state that sells them to the public. I got my last AR in PA and I live in NY(Westchester).

Correct me if I am wrong about this one, but I thought someone posted a thread not too long ago stating that in AZ you do not have to be a resident to get a CCW, all you have to do is take the two day safety course and you will be issued a CCW permit??

Quoted: You can establish partial residency in another state if you own a summer home and then you can buy anything legal in that state reguardless of your home state's laws. The only catch is that you must keep the weapons where you bought them, or register them in your home state if allowed.