not sure on this one really firstly, when ever the car breaks at my house ( mum and dads car, my car etc) how would you get the ca to the place in the first place, would need a recovery truck etc - then while your away you would have to leave other customers at the unit, so you would then need a second person to manager / help people that are already there. secondly you woudl have all the other problems other people have mentioned.
but yeah i would rent it out etc if all was priced ok