Kevin, as has been said, with your budget a dealer van is probably not an option, BUT there are good vans to be had privately, but you will have to be very careful with what you buy.Damp and general water ingress are the main caravan killers, and repairs can be very expensive, so make sure you check every inch of the van, both inside and outside.Look for stains on the walls especially round windows and press the walling of the van on the inside ALL round the windows, especially where the grab handles are located, it should be firm, with no sponginess at all.Pull the external grab handles, if they give, you have problems, water has got in behind them and rotted the timber.
As you walk on the floor,feel if it is solid under foot, or is it springy/spongy? Check that all the appliances work. Check the wheels and tyres, how long has it been out of use, how has it been stored? what condition and how old are the tyres? Caravan tyres very rarely get to the point of low tread, its the sidewalls which give out before that, and generally tyres should be changed at the very latest every 5 years, before if showing signs of bad sidewall cracking.
Finally, try and make absolutely certain that the seller IS the legal owner of the van, ask for all the documentation and receipts for it, and if you buy, get a signed receipt from the seller confirming that they have sold the van to you.
Insurance is a very sensible thing to have, especially if it gets stolen!!!