On my last visit, I was comfortable asking them to start at the rear bumper and work their way to the front bumper inside and out.
This should be done buying any new or used RV from a dealer,If they won't,go elsewhere.See absolutely everything work and inspect the roof.
Make sure "everything" is as you want it before you buy it.Once you buy it,it's yours along with the minor fixing most RV's need from time to time.If you can't fix minor things,you do not need to have an RV.
I can't imagine taking an RV back to the dealer for minor fixes.