I looked at a few recently , my son printed me off a check list that he got off the internet , there was a number of known faults to look out for , it would be worth having a look for it , the three I viewed all had expensive to repair faults but in fairness my budget was £3k , the good thing about the list was it gave you a sequence to go through that otherwise the fault would not have been found .
From memory O rings on the heater matrix were a common problem which resulted in dampness on the carpets, air suspension not holding was another , air conditioning, and of course rust in chassis .
I’m sure there will be plenty of help on here .,