First find the MH you want and then get professional inspections done. If you don't do this
BEFORE you purchase, you run the risk of spending significantly more
AFTER the purchase. If something is found, you can then decide if you want to proceed and can use it to negotiate a better price. You will be going into it with your eyes open. IF nothing is found, GREAT!!
Before you finalize any purchase, I would suggest that you get an independent certified RV mechanic to inspect all the RV systems, including the roof. In addition I would have the engine, transmission, frame, etc. inspected by a diesel service shop. Having a coolant and oil analysis by a lab (like JG Lubricants ) would reveal any hidden problems.
Make sure everything is in writing!! Any purchase should be contingent upon successfully passing these inspections/tests.
I would do this to any used MH I was looking to buy.
Buy an Engine Oil Analysis Kit Today | Engine Oil Analysis Service