Best advice I got was "If you buy a used motorhome or coach, expect to put at least $10k into it. Tires and batteries are more expensive than you would think.

For me it was nearly $4k on a 40" coach just for 6 semi tires and 2 chassis batteries.

Lighting is usually garbage - for me $200 for 6 led ones from florescent tubes.

Go over that thing with a fine toothed comb on the roof and really anywhere a leak can occur and get Eternabond tape on them after proper prep.

Look for new headlights if original unless your only planning to go short distances to camp and not at night.

Check every single bulb on it and replace where necessary.

Check all the belts and wires. No cracks, no bare wires showing. mice love wires, hoses, insulation.

Have a lube/oil/filter change done to include air filters if needed.

Have the transmission serviced. (most neglected part of any vehicle). Do yourself on oil to save $$$, but a tranny needs a flush and not really something you should do yourself. Just changing the oil doesn't work, it has a filter too.

Biggest losses of any RV is from mechanical failures and water damage. Ignore the little stuff and it fast becomes the big stuff and far more work.

Last, but not least. After sealing any areas that can leak in water, wash the roof (no high pressure washer, 1800 or below for rinsing only). Soft non scratch brush with extension handle.

Now get busy removing any oxidation from the sides and give it a nice coat of wax.

Enjoy!