OK, to buy and sell modern guns of any kind, you need to get an FFL and keep books and records as required. Most of the info you need is on the BATFE web site, at www.atf.gov
. Before issuing the license, BATFE will require that you have a place of business that will comply with local zoning laws, etc., and that you have the required business licenses. Information on the latter can usually be obtained at your local town hall or county courthouse. Small towns often have few zoning laws, but they also have local "customs" as to what kinds of business are OK and where. If there is no precedent in the town for a gun shop, you might have to appear before a zoning board or the city council to try to show you are not some nutty "militia" type. (In this kind of thing, relatives and friends help; it helps a lot if your father is the mayor and your brother is chief of police, for example.)
As I said before, you will be better off with a storefront, even if you could work out of your house. If you have a local community college, check to see if they have a small business course, and if so, take it. Also check on a machine shop course; it will be worth while.
If you plan to be a stocking dealer, you will need some cash or a line of credit to get started. Even if you just buy guns from the local populace, you will still need money for that and for your bluing equipment if you decide to get into that.
You will need someone to do your books and keep you out of trouble with the IRS and state tax authorities. (You will probably be an S corporation, wholly owned.) I do recommend incorporating, as that way if something goes wrong, liability falls on "Shawn's Gun Shoppe, Inc." and not on Shawn Dow himself. You will also need insurance in case a customer shoots a hole in your roof or you let a round go in the wrong direction. Also, if you have custody of customers' guns, you are liable for theft, loss, or improper work.
Sticking to long guns may make things easier; it would in some states, in others it makes little difference.
You should consider talking to an attorney or at least someone familiar with business law in your state.
Believe me, the FFL is the easy part. The rest can be hard or easy depending on a lot of factors.