Tires on RV are not the same as on your car or light truck. They do not have the same UV protection. As a general rule, tires over 7 years old should be replaced. Watch when you buy tires and check the date of manufacture. It will be a four digit code on the sidewall near the DOT symbol. The first two digits are the week of the year and the last two digits are the year that the tire was made. So a 5109 would be the 51st week of 2009. Have you checked your tires?
When looking at a RV you will want to run the Air Conditioners for at least 10 minutes. Then with a food grade thermometer take the temperature of the incoming air (about 5 minutes) and then at the vent closest to the air conditioner take the out going air temperature. You are looking for a difference in temperature of about 20 degrees F or more.
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.