[sourdough]

Where you are the VERY first thing I would do is look at the roof and all the sealing around the edges. Cracks, voids, splits etc. would indicate possible leakage somewhere inside. From there I would look over, under, around and through the cabinets, closets etc. for any sign at all of water leakage; wall coverings pulling/hanging loose, stains, soft floor/walls/shelves. Water damage and all the misery that can cause one is something to search for diligently before buying.

After that, tires, bearings, brakes, lighting, battery(s), furnace, AC, water system etc. You really should take an inspection list (don't know where one is on this forum) and use it to go over the unit with a fine tooth comb. At 13 years old and just sitting there is no telling what could be wrong unless you "dig into it". Good luck.