Older motorhomes - Advice on buying please.

I've been looking through the classified ads on the clubs website and keep seeing vans from the late 90's early 2000's for between £6 & £8k.  These ads are all listed as private sellers.  

I'm keen to get some advice from people who have vans of this age  to see if they have any life left in them or if they are likely to be mouldy damp money pits.

We currently have a caravan so we know the basics for checking for damp ect and I'm handy with spanners for the oily bits, however I'm keen to get some real world advice or experiences that you've had.

Many thanks.