As previously mentioned, check the age of the tires. RV tires usually age out before they wear out.
Check for evidence of leaks (stains, soft spots on floors, etc.), a small leak can cause a lot of damage if not repaired quickly.
Condition is very important when buying a used RV.
If I can't test drive a unit, I would not buy it.
If you can't check all the systems yourself, pay a RV tech to do the inspection. It's money well spent.
Do not be in a hurry to purchase. Take your time and do your homework.
There are a lot of units available.
Let us know what you buy. But take your time. The right unit is out there waiting for you.
Enjoy the search. :)