The key to any MH purchase is how it was maintained while it was being used and how it was kept when not in use. If left sitting out in a field between very infrequent uses, that is not a good thing. Perhaps rodents could have gotten inside or been nibbling on the wiring. The same coach that spent it's time in covered storage would probably be in better condition.
Some things on a MH deteriorate based on mileage and some just based on time, like belts, hoses, and tires.
When looking for a used coach, check the records and look for one that has been regularly serviced and stored under favorable conditions. Also keep in mind that the past weather issues may mean coaches are for sale that have water damage. A complete thorough inspection by a mechanic and an RV specialist should reveal any issues.