Buying a unit that old, you will really need to have the condition of the roof checked by a professional before you make any commitment. It can be a really expensive lesson to learn.
Make sure that, when you go see it, the current owner has all the capabilities for you to test all the systems. Won't do you any good to get someplace and then find out the plumbing leaks in many spots. Same with propane. Electrical system, furnace/AC. If you're lucky you might even be able to make sure the waste tanks don't leak.
