Let me comment here on the single action revolvers, leverguns and other "cowboy action shooting" stuff: to really attract that scene, you need to first UNDERSTAND that market and second, stock a solid range of the accessories. You need at least a passing familiarity with what's competition legal in both guns and accessories. If you do those things, there's huge money in that and related fields like civil war re-enactment and the like.
If you don't do those things, don't bother. With the caveat that some SA revolvers are more "hunting guns" (Freedom Arms, Ruger's adjustable-sight SAs, etc.) and ditto leverguns (Marlin Guide Gun in 45-70, the various 30-30s, etc). Most SA revolvers and leverguns these days get sold for CAS/SASS sports but for sure, if you're going to be selling "hunting stuff" depending on the local market, some SA/lever pieces will fit.
You might be best off picking one or maybe two main "specialization areas", such as:
* CAS/SASS
* Hunting
* Personal defense/CCW/"tactical".
* Shotgun sports/birding
There's others (benchrest rifles, muzzleloader folks, etc) but the numbers are much smaller and they're more likely to mail-order.
Believe it or not, some of the customers of one of the above categories may feel sketchy about even walking into a place that does another. Sporting shotgunners are notorious for getting hinky if they see a lot of Glocks/ARs/etc. CAS/SASS too to a lesser degree. Which of these areas are you personally best suited to cover? You CAN try and cover all of 'em but...you likely won't cover them all very well and you risk not covering any well enough.
The other thing is, start thinking in terms of selling complete systems - gun plus holster plus recommended target and "business" ammo (hunting or defense). You might even offer complete packages whereby somebody gets, say, a low-to-mid-range 1911 family for carry and at a discount, a Ruger 22/45 which was designed as a cheap-ammo trainer for the 1911 family. Offer a discount on the whole package, both guns plus holster for 1911 plus a starter ammo set...what us computer geeks called a "turnkey solution" 20+ years ago.
And trust me: computer marketing is so much more advanced than gun marketing it's not even funny.
Another thing...some people are going to freak out over ammo costs and rightfully so. Get a cheapo computer, load the following video on it:
http://www.youtube.com/watch?v=noFKV8S6cnQ
Show that and STOCK THOSE!!! Sell 'em all day for $25 a pop plus some basic supplies (primers/bullets/powder) for each caliber. People will be more likely to buy the gun if they know they can feed it on the cheap with reloading gear cheap enough to pay for itself in the first 100 rounds. Let 'em buy the first 100 rounds of factory loads and recycle their shells.
Look...think of the term "FUD" - Fear, Uncertainty, Doubt. You want to eliminate those. "Yeah, I got a holster for that thing, several depending on where you want to carry it." "Yeah, I have ammo that'll work great for that size gun." Etc.