We bough a 16 year old coach in good condition in February. We've been on 6 trips so far. Here's what we experienced.
First trip the water pump would not turn off. Turned out to the the latching controller--cheap and easy fix after diagnosis.
Second trip, water leak in the basement. Cheap fix, but I ended up having to tighten up all the plumbing connections in the basement.
Second trip, leak in bathroom vanity feed line. Cheap fix.
Third trip - it became evident the front A/C unit wasn't cutting it in high temps. Replaced @$1,200.
Fourth trip - fuel filter clogged--caused engine to miss. Replaced two fuel filters ~$100.
Fifth and sixth trip were uneventful.
This doesn't count about $750 in routine maintenance I've done. I still have another $750 to do before I'm finished. I did all the required maintenance this year, even the every three or four year type so it would be cheaper each year from here on out.
We are looking at some expensive maintenance when we replace the air bags and shocks down the road.