Don't know how it works in your area, but a friend of mine regularly buys vans for work by calling school boards/schools. He managed to get well maintained vans for a good price. If you're going cargo vans, definitely go maintained vans. HOWEVER, keep in mind that, at least around here, maintenance/service vans have their engines running 24/7 or close.
Another suggestion is to look for a Chevy/GMC Rally van. Had 2 mid '90s, and both were bullet proof. Regret selling the last one, which even had a raised roof nonetheless- used it for 2 years, then sold it for 50% more than I paid for it (but got it to run like a Swiss clock, everything was perfect- other than mileage, but what can you expect from a 7.4l gas engine).
no snowflake ever feels responsible for the avalanche...