Get the date codes from the tires, repack the wheel bearings BEFORE you hit the road. Unless the owner can prove it was done in the past year. If the tires are more than 7 years old by the DOT codes
plan on replacing them before you start the drive. Also check the date codes on the LP tanks
, they have to be less than 12 years old if you are going to be able to have them filled.
Make sure everything works to your satisfaction. Check for soft spots in the floor around the corners and edges, also look at the seams on the top for clean solid caulking.
Those are the main items that come to mind at the moment.