Since you are contemplating being a dealer and renting machines I suggest you get on the forum for that brand of machine and see how others are doing with this concept. There is a shop an hour from me with an APQS dealer, that offers rentals but I don't see others in there using the machines the time I have been at the quilt store.
I know apqs and gammil have forums. you might also check
www.mqresource.com which is a machine quilter's forum.