I volunteer with a non-profit photographic gallery, and we have a rental darkroom in Brattleboro, VT. It's not a large place, google says the population is 12K.
For us, it's a labor of love (and tradition) rather than profit, it doesn't truly earn its keep. Unless there are a lot of people in town who are interested in darkroom work, but can't for whatever reason, do their own, I think it would have a hard time making expenses. One angle I'd suggest is having some unique equipment, like perhaps and 8x10 enlarger if you can get your hands on one. A good UV exposure unit would be good too for folks who want to use alt processes.