Basically, you will need to spend around £3,000 to £5,000 for something you wont be under all the time.
If the car has power steering, check the drop arm for leaks. A new box will cost around £180 - £200, plus the time to fit it.
Check the hubs for leaks, replacement seals are about £60-£80 per side.
Bushes are cheap to replace, but can be a b!tch to get out the old ones!
Rear chassis cross member check for rot, especially around the jacking points. Replacement would be about £150ish.
If the engine is breathing heavily, be careful.
Check for transmission whines and make sure it changes up and down OK.
Check the transfer box to ensure it engages correctly and drives OK.
Bulk head rot, expensive to replace.
Doors rot, especially the wind up window type and very expensive to replace.
Be prepared to travel to get a good one.