To the OP:
I applaud your courage for planning to open a small business and go it yourself. I don't know where you are located or what your community or competition is like. I am NOT a small businessman, so take this for what it's worth.
I have two small LGS within 20 miles of me. One is - literally - a cop shop. She caters to police officers and her stock is mostly combat-style guns: XD, Glock, Ruger, Smith, a few Tarus, Beretta, and a couple other major players, all in the $450-800 range, pocket guns (j-frame, Kel-tek, etc.), and other personal defense stuff. She has identified her target and she stocks to please. She has one or two single-action revolvers, one or two larger DA revolvers, a couple .22 plinkers, but those are obviously 2nd tier in her sales. She stocks a little hunting ammo, but LOTS of personal defense ammo: brands, calibers, and "flavors." She does not trade; all new sales. In her cabinet are probably 50 or 60 pistols, 90% autos. She has about 20 or so long guns, a few of which are few hunting rifles (mostly Savage & Mossberg) but most are "black" - shotguns, ARs, and a couple "niche" guns - FN, Saiga, etc. There is also a lot of other LEO apparel & supplies (cuffs, batons, etc.) Her business isn't exactly booming, but it is steady...there are always people in & out.
The other is a "good ol' boy" hangout. He has about a dozen or so new handguns, almost all are "low" end of the price scale (not necessarily quality!)- taurus, Rossi, and Rock Island. Might have an XD, Glock, or Smith or two, but not much more. He trades and sells used, but even his used is...well, USED! Long guns are not much better, both in quantity and quality. I stop by when I am in the area, but I don't make a special trip there. Ammo choices are slim as are parts. There are a couple good ol' boys who hang out, but customers are pretty few. He does a little gunsmithing - the kind of stuff you & I do for our own guns - for folks who don't care to do it themselves: cleaning, scope mounting, etc. I hate to say it, but I don't know how long he'll be open...
The first store is in a small pass-through town; the second in a good-sized town. Why does the one do well and the other just exist? My guess is it has a very precise market and has targeted that market as its goal. She does a little "side" stuff to cater to the locals who need something (including a Hi-Point or two), but she has not lost sight of her goal.
So, that's my 2 cents...find your target and stick to it. Don't try to be all things to all people - unless your community truly is gun shop-less. In which case, start with Target Group A with a tease towaard Group B and then add a second focus later.
Good luck! Hope it works for you!!!
Q