Reliability, now there is a word. You see problems in brand new coaches as well as older coaches.
Ours is 20 years old and we have had a hydraulic pump failure. Other issues were minor and all fixable. At 20 years old no leaks from any component on the MH. It is a Beaver and seems to be built well.
Do expect extra costs as mentioned in filters and larger amounts of fluids. Try if possible to find a unit with new tires or negotiate price based on tires if possible to avoid initial sticker shock at purchase.
Do your own work and save a bundle plus it is rewarding.
Pogoil.