Buying a Former Rental Class C. How many of us out there?

I personally would avoid any rv that has been leaking. You have no idea how much damage the water has caused. Find a dry one and keep up with the maintenance for the cap seals.
The other option is to find out if they will completely repair the damage... But you have to be sure they took care of everything.

Per the "noise, vibration, and harshness" issue. A lot of this is going to be normal. Think of these as uhaul trucks as opposed to passenger vehicles.