Rust should be OK if washed a bit over its life – mines 6 years older and barely a spot, never been welded for MOT etc.
Cambelt is a must. If you don’t have good evidence, factor doing it into pricing.
I had a real issue with glow plug relays and starting (why the previous owner sold it .. but I paid 2K for a very solid van so I bet on fixing it) – eventually traced to a faulty temp sender, clipped the pin off the 1351356346126th gp relay (most melted as they were locking on after post warm .. 40A thorugh it!!) and its been golden ever since. Keep meaning to do the sensor but apart from running a little rough for the first 5 minutes, it’s been solid.
Good road test to listen for suspension knocks and bangs, changing bits of that have been my biggest expense.
Check steering lock to lock .. probably worn.
Which engine? I have a 2.4 AAB – no turbo so slow, but reliable (or at least thats what I tell myself as I chug up the hills). On 180K now.