I've heard that if a diesel has enough compression to start, you're ahead of the game
For an inexpensive car, you can decide spend lots of $$ to repair/replace every little item, or DIY and "run what ya' brung" until it's time to donate it to the local charity motors lot. It might surprise you and everyone else by lasting a lot longer than you'd have thought.
If the car price is REALLY low, you've got very little to lose, except state license fees, etc. so it could be a real cheap date.
Good luck in either case.
'96 E300D 60k mi (wife's daily ride)
'95 Audi 90 120k mi
'92 GMC Suburban 139k mi
'85 300SD 234k mi (my daily ride)