It really is a buyers market at the moment and so a bargain could be just around the corner. I have little knowledge of the TD5 but the the 300tdi is probably the best bet considering your budget. Early ones had cam belt issues but that should be long gone, second gear on the R380 gearbox is a little weak, check everything electrical as something simple as the central locking not working could cost money and headaches.
As already mentioned RUST inner front wings, rear seat belt anchorages, boot floor and anything else you can check, the old magnet trick is good for finding hole filled with fibreglass and filler.
The rest is usual i.e leaks ect, anything from the gearbox/transfer box may indicate they have been run dry?
Without doubt there are many on this forum with loads more experience so watch this space,
regards
Dave