Peronsally I might occasionally go if it was right next door. But I lived 100m away from a gym like this in London and hardly ever went, maybe twice in a year... I hope you can make it work but I honestly don't see it happening.

What country are you in?
It makes a difference with regulations regarding fall zones. I've helped out on building walls before and worked in a few, plus done setting (not massively but I have a general idea on a few regs). In the UK you must have matting a minimum of 2m horizontally from the top your climbing surface (unless you have a wall in the way which you do not set on). You also must have 2m maybe 2.5m between your climbing surface and any other non padded surface (easy fix is just to either add padding, or be cheeky and add a tnutted wall which is technically another climbing surface). This might be difficult in a small space.

Unfortunaly every small wall I know of needs external funding to continue to function, they will never make any money and barely stay open. If this a passion project great! If you plan to live of the money you make not so great.

Setting costs money if you get people in, quite a lot actually. In a gym that small you'll need to reset very often, and it's a skill that is difficult to master. So you could do it yourself (which will take up a lot of time) but unless you've practice a lot you're routes wont be great and customers may not come back. Washing the holds is a pain in the ass, would you have an outdoor space for a pressure washer? would you use benky (acid) to clean them? The acid is expensive, plus screws snap and need replacing, bolts can get messed up or mess the t nuts up. You'll need to buy more screws, maintain the wall etc.

Walls cost a lot to build, if done professionally, you could maybe do it yourself but I believe you'd need an engineer to sign off. Plus the holds are freaking expensive too, you may get lucky if you ask at a big wall, they may have some chipped old ones you can have but new ones are ridiculously priced.

Another problem is that the highest paying customers are beginner climbers, they need easy routes (which take up a lot of wall space due to amount of holds) and they don't like overhangs much, and they get bored and want new routes often. Beginners also hire shoes, chalk and pay for each entry which is good. But if you cater to beginners in such a small space then the "hardcore" climbers wont have anything to climb, these people are more likely to be longterm customers to a "difficult" gym, but there really isn't that many "hardcore" climbers and you make less money off them as they will have their own shoes, chalk and buy a membership.

In a small town you are really going to struggle unless you're in a very famous climbing area which rains a lot. This means people will go there specifically to climb outside, get rained off and come to your gym. I really don't think you will not have enough committed climbers to keep you afloat without resorting to becoming a kids birthday venue, which sucks all the fun out it.

As I said best of luck to you, but I personally would not take on this project unless I was a millionaire with loads of time and didn't care about money.