When looking to buy an RV start with a roof inspection. You will need to bring a ladder, trust me, the ones that are attached will not be good enough unless you weight less then 150 lbs. Get up on the roof and start in one corner on your hands and knees and inspect all of the roof. Looking for holes, torn material, caulking that is pealing apart, broken vent or AC covers etc. If the unit has slides, check the seals while they are in and out. Do you know that most owners of RV never get up on the roof! This is were most of the water damage starts. If you find something that doesn’t look right, make a note and check the inside real careful when you get down.