I swear there was a thread on this exact thing about a year ago, I did find the one where Cordell a brainstorming thread about opening a shop. http://www.columbusracing.com/forums/showthread.php?t=110583&highlight=lift+rent
I think the biggest issues would be insurance because of the potential risk of have some one using tools, possibly power tools and not being trained mechanic. I'm not in insurance but that seems like a big liability. The other issue you would definitely run into is have a car up on a lift, half apart and something breaks/new parts don't fit etc. and the car can't be finished before close or possibly until the part arrives days later.