To be honest I think it sounds like a great idea, I would love to have a place like that right now! Would you just have a huge air compressor they could hook up to or would you rent tools as well? Also would depend on if you live in a rural or urban setting. Would you rent bays at different rates? 1 day X$, 1 week X$$ and such (I would assume so)? Also you might need to have some sort of waste container for oil and other such things depending on where you live.