I run a small pawnshop in Madison, my wife is a teacher in Eatonton, and I've lived here for over 20 years. I think you'd really like the area, but the population is a little sparse for another gun shop. There's 2 pawnbrokers in Madison, another in Eatonton, a new one out at the lake, and yet another in Greene County, all of which sell guns. That doesn't include the kitchen table guys, or the guys that do it under the table, I suspect there are probably another one or two small shops that I'm not aware of as well.
There is virtually no industry, and good paying jobs are few and far between. I doubt you could scare up more than 50k people in all three counties put together. But if you are bound & determined to have a go at a gun shop, don't let me talk you out of it. However, I suspect you'd have the best luck living in Putnam and opening the shop in Milledgeville, as the population is much higher down there.
I sent you a PM with my phone number at the shop. Call me if you like, I'd be glad to answer any questions you might have.
Hope to hear from ya!