If you are legally a resident of VT, you could either buy one face to face (lots of guns can be found at yard sales and such in VT) or buy one and have it delivered to you if the seller lives in VT also, so it never crosses state lines. Keep in mind many sellers on those sites are in fact FFL holders, who just happen to use those sites to sell. And many will not ship to a non-FFL even if it's within the same state, despite the fact that it's legal. VT's minimum age to own a firearm without parental consent is 16. Federal law basically says you must be 18 to possess/own a handgun. You can't get ammo for a handgun either from a dealer until you're 21, so that'll be another hassle (though many handgun rounds are used in rifles, and dealers may at their discretion sell it to you if they believe it's for a long gun)
If you are planning on leaving VT after a few months or so, and returning to another state as a home, you can't legally buy a handgun in VT, only a long gun (this is federal law) since you can only buy a handgun in your state of residence. You could legally buy an "antique" (something made before 1899, or a modern non-cartridge firearm, such as a cap and ball revolver) right through the mail, no FFL involved. Keep in mind some sellers of these guns still will ask for proof of age, possibly of being 21. If your location and state of residence, as it says under your username, is New Jersey, you'll have to buy a handgun in NJ, and NJ has very strict laws, as you may already know, quite different from VT so if that is your state of residence, things are complicated.
