Depending on where you live, if you do a feed and tack store, you may have a shot.
I live in Los Angeles and of the 6 local horse stores (all within less than 15 miles of eachother), 4 are feed stores that sell hay, grain, shavings, as well.
I worked for 10 years in a popular feed and takc store and while the original owner was a business man, and this store was able to support 2 other stores he opened... he sold the store and within a year and a half the new owners ran it into the ground and it closed. There were some major issues there as far as paying rent, etc, but tehey bought a lot of junk to sell.. Like, they had bought these necklaces for $10 each, then priced them at $25 each. They were something a 10 year old kid would make at summer camp. We never sold any of them.
So it's being smart about your stock as well. The orginal owner was smart in that he'd only cary maybe the 6 most popular fly sprays. Yeah, we'd have people ask for stuff we didn't have, but it wasn't worth buying a case of 24 when we'd only have 1 person every 4 months ask for it.
We were also the only local Circle Y seller, so if someone local wanted to try on a Circle Y or buy one, we were it. They also did a blanket cleaning/repait service, and while I think he barely mad a profit on it, it brought customers in. Oh and they did tack cleaning and repairs and custome orders as well. But that was kind of hit or miss, because sometimes someone would order a headstall, the guy would make it (he does beautiful work!) and they wouldn't like it. Yeah they'd have put a non-refundable deposit, but the store still had to purcase the item and then put it on the shelf. So stuff like that would sit.
So it depends on the area and who your customers are. Just remember, hrose people can be crazy. ;)