I would pass on the former rental. No guarantee just because it was commercially owned that the maintenance was more than the minimum required.
Personally I would not buy new. 2-5 year old coaches seem to be in the sweet spot for used. Low mileage and general usage. Maybe a bit of warranty remaining and the former owner worked out the initial problems. You can step back even further in time for something older but you'll need to know what to look for regarding what to avoid such as water damage, low mileage but heavy use.
A 17 year old coach with a dealer warranty is a bit like life insurance on a 71 year old male who smokes, needs insulin and is overweight. If you can find coverage the cost is either going to be very high or the mice type very detailed concerning what is not covered and other restrictions.
The savings on a 2001 against a 2012 of $15K is pretty light. Should be double if not more so it doesn't seem like much of a savings. Shop around more and don't be afraid of spending $500 on airfare to check out a coach that might save you $5000.