I always thought it would be fun (yes I said FUN - as in it's not something I really plan to do or would think about making a living on - just FUN to think about
) to have a little gunshop and trade largely in used firearms.
When I lived in MN there was a great hunt'n and fish'n store on Hwy 65 just south of 10. They had plenty of new guns, but the best things was that they had an OUTSTANDING selection of used firearms that turned over very regularly. I'd stop just to browse the new arrivals and would always leave with something - even if it was just more ammuntion.
It helped that their customer service was awesome. I bought several firearms there, a couple of which could probably have been had at Wally World a little cheaper. But I liked the place (wish I could remember the name so I could give them a plug