OK, there's a lot of confusion in this thread and I'd like to explain how things work in FL as someone who is a resident of both MA and FL. I am not a lawyer and can only speak of my experiences and understanding based on researching residency laws listed in the ATF, talking to the Dept of Agriculture (which handles permits in FL), and talking to LGS in FL.
1. Residency in Florida is a fluid thing that depends on the area of business/government. Example: Residency for in-state education has different requirements than taxes than car ownership etc. Wrt gun ownership it follows the federal law. If you have property and are in the state you are a resident. However, some LGS will have different rules - some require a state picture ID, which would mean giving up your MA drivers license. Of the 3 stores I like to frequent only 1 requires picture ID.
2. Owning guns. Anyone who isn't a felon and is a resident can purchase and own a gun. You can have it for home defense and you can drive it locked up to your range without requiring a permit of any kind. You need a concealed carry license to carry concealed. there is no open carry in FL. There is no concept of resident or non-resident permit, my address is not on my FL permit. concealed carry is more limited in FL than it is in MA (Shocking!). A nice bonus if you're a resident is that having your permit waives the 3 day wait period when purchasing a hand gun.
3. If you have a residence and you go to buy a firearm you should take a copy of a utility bill or property tax bill to prove it. Some places are tied into the local county database and can look it up on the spot, some can't.
4. Pawn shops are usually FFLs.
5. I am domiciled in MA so retain my LTC. My Florida permit, as I mentioned, is not resident specific. When I change my domicile to FL I will give up my LTC and if I wanted to carry in MA would have to get a non-resident LTC.
Again, IANAL, this is based purely on my own personal experience and reading. Honestly, in FL no one seems as hung up on stuff as they are here they think MA laws are idiotic and take delight in pointing out the stuff I don't need to worry about.