Wheel bearings are not usually a problem, as vans don't do that many miles, if its been stood for a while then brakes binding on can be a problem, and worn brakes can only be properly checked by removing the drum. The normal comment of "a good service history" probably doesn't work on a van of that age/price !!
Not that much to a van chassis to be honest, if you want to check that the "rubber in tension" suspension is good then a tape measure at the wheel arches is easy .. if there is a MAJOR difference in height that could indicate a problem.
Tyres should be changed every 5 years regardless of wear .. so a knowledge of the DOT code to check dates on tyres helps.
I doubt the seller will let you power everything up, including the water/water heating/central heating/fridge/cooker systems ... but they are all things that do go wrong and can be expensive to fix ... 12V electrics is actually quite easy / cheap to mend .. unless master control panels fail ...
HTH