If you want a nice working van you have to go looking on the streets and somewhere that's not California its just on Craigslist your bound to get fucked
YES! rule #1, don't buy any niche vehicle (VW, conversion van, "sports car" or fixie bicycles for that matter) in California - your paying nearly 25% more just cause of what it is and where its being sold at; California - go to washington, oregon, idaho, nevada, arizona, new mexico or colorado.
Rule #2, don't buy from someone selling more than one vehicle at a time, often they are in a vacant parking lot, never at their home residence, be sure to ask "do you have anything else?" They will asume you are asking for other vans (if thats what your trying to purchase) and will offer something like "No other vans, I got a 79 BMW and a dodge 2500 diesel" these are shitty people selling vehicles for profit, not cause they no longer need/have use for or want said vehicle, they are like a dentist offering you a pearly white veneer in stead of a steel crown - they are trying to turn a buck, they could care less about you after they take your money, and honestly I have been a lemon mechanic and done horrible things to make cars sell fast . . .
Rule #3 I think its already been stated, keep away from something that has been sitting for a while, NOW there is a way to properly go about it, UNDER NO CIRCUMSTANCES EVER LET THE SELLER "FIRE IT UP FER YA" tell them that if they turn that starter you will not even consider the sale, brake parts excluding, the most important thing is the piston rings, when the oil seeps low in the crankcase the spring steel rings eventually fuse to the piston sleeves and when they are broken free from rotation it brakes little chips in them; this means that significant blow by is in the near future, this means lower MPG, overheating potential, oil consumption, and scoring of the sleeves which furthers the damage and it eventually will need a complete rebuild or replacement engine.
Now, the way I was taught was to remove the spark plugs and put roughly a tablespoon of automatic transmission fluid in atop the pistons, similar to
this post
but the important thing is that the rings are lubricated, leave that shit in there for at least a day or more before you attempt to turn the motor. I have successfully revived many old cars this way.
Personally I swear by G series GM vans, my current is a 1995 GMC 2500, but I've mostly had Chevy's anywhere from 1975 to 1992 and they are alwase a charm to drive, spacious to live in and easy to maintain.