Our RV is a 1990 Winnebago Warrior Class C.
Our roof was shot - previous owner had coated the entire thing in Heng's Roof Sealant or similar. I just do the same thing and it's mostly water-tight. Had a leak in the sunroof over the shower but I just gooped over the cracks.
Headliner disintegrated - I pulled it all down and glued up fiberglass paneling.
Fresh water pump died; I replaced it.
Control board in water heater died; replaced with Dinosaur Electronics board.
Control board in fridge died; replaced with Dinosaur Electronics board.
Had to have cab AC fixed and converted to new refrigerant.
Genset didn't work when we got it 10 years ago - $500 to fix.
Just replaced all electronics on the genset last year - $500 more.
Had to replace Ignition Control Module for engine last year.
Had to replace radiator last year.
Had to have engine water pump replaced a few years ago.
You better be handy or have money if you have an old RV.
I'd like a newer one but we'll never be able to afford another one so I just keep it limping along.
Steve