I JUST BOUGHT A FIX IT MOBILE HOME IN FLORIDA they painted over the pneling and it has all wrinkled/bulging/bucking and separated from its backing... what would cause this?

The mobile has been sitting for 3 years at least not occupied... could it be the heat, moisture, paint?

Combination of those along with improper preparation before painting.

Florida gives new meaning to the word damp. The paneling would buckle even if unpainted, especially if unoccupied for 3 years.
The entire structure could easily be rotten. Call 3 contractors for estimates and they can tell you what's what. Floors go even faster than walls.

Thank you very much... I will take your suggestion and call contractors to get an iea of what caused it, hope it is nothing to be too alarmed about?

What would you suggest doing the walls with I wanted to do knotty pine wall planks tongue and groove. Go over existing wall without stripping. But the wrinkles/bulging is going to be a problem doing anything to them unless I rip it all off.

If you plan to live in it.. get what you like. If you plan to flip it or move shortly after.. find something neutral and in vogue currently and not too expensive because its still a trailer and you'd never see much of a return on investment from that work. I'm personally not a fan of layering new stuff on top of old stuff.

I agree... but I also do not think a 1968 mobile is worth the effort to strip everything and then refinish. Maybe I am looking at it wrongly?

I think you owe it to yourself, no matter what your plans are for the trailer, to just rip that panelling off and see what is going on behind it. Probably if the panelling is that bad, then you can bet something else is lurking behind it too.

I also think you should rip it off and start over. Materials cost is the same... but the extra work to locate the screws/nails and making everything fit in corners, windows and doors on top of the other material offsets the work to remove it. Plus you have the point Tickle raised.. not knowing what was going on behind it.