Technically, they DO know what they're talking about. No, there is no real official "dual residency". You either live in one place or the other. But special circumstances can be granted to recognize that you can interchange between states without filing change of address, changing driver's licenses, car registration, etc etc over and over again.

I had an instance once where I was driving my "Texas Truck" while living in KS. A sherrif noticed that our company had a lot of vehicles with out of state plates parking there for quite some time. The laws in KS stated that if you're living and working in a state for 90days+ then you are required to transfer your tags and update your address, essentially updating your residency as a Kansan. My company employed a lot of temporary contractors, including myself, so even though we lived and worked in KS, we never actually moved there. I was a somewhat special case because I maintained a KS driver's license, as well as a KS address and vehicle registration.

It's actually a VERY convoluded system based on what rules are in effect in which state. To tag and insure my truck in TX as well as get a hunting license in TX, all I needed was a physical address (not just a PO box) and "proof of residency", which is basically having my name on a bill at that location. In KS, proof of residency is more stringent. The State of KS had to yield to the TX law that even though I maintained a KS address, and KS driver's license and car registration, the State of TX still recognized me as a resident.

Technically, once you're 18, you're actually MOVING back and forth. The only way "dual residency" works is if one state or both have short or lax residency requirements. In KS, they want to keep residents, so if you do more than stay in a hotel here, we want to make you a full-fledged resident, but if you move, you basically have 6months to cease residency in KS (you're considered a KS resident if you spend 1 day over 50% in KS that year, and you're required to BECOME a resident if you stay in KS longer than 90days). Other states are more lax, like TX, where if you keep a physical address and get bills as if you lived there, you can qualify for residency there, but aren't required to spend "1 day over 50%" there.

What it comes down to is that your legal residency is base on whichever driver's license you hold. However, some states let you live there LONGER without changing your drivers license. For example, Kansas is strict. You have 10 days following a move (registered at US post office) to update your drivers license. This is true even for Kansas residents moving WITHIN KS. TX seems to be much more lax. I was pulled over a few times while I was licensed in KS and living in TX. I just said "I live up in Denton, here's my current address, I just haven't updated my address...". So I basically always had to keep my license in KS.

So I guess the moral of the story is, if you really expect you'll be moving back and forth, read your individual state's laws closely.

Also, remember, for college tuition, you may be required to prove TERM OF RESIDENCY. In Kansas, universities require one continuous year of residency prior to enrollment to qualify for resident status. There LITERALLY is no way around this. So if you tried to play a "dual residency" game and bought a gun in FL as a resident and effectively prove your FL residency, you would be discounting yourself from qualifying for resident status in IN. Of course, this only applies to the year PRIOR TO ENROLLMENT. Once you qualify as a resident, then you're in for the rest of your term.

The easy way around that, since it sounds like your PARENT will be living in FL, is to have them buy the guns for you. It will NOT count as a "straw purchase" since they are your parents.