Buying a car that runs well is a good starting point. Cars that have sat for years are an additional headache renewing every part of the fuel system. Maintenance records are gold. Lots of bits need renewing as they just wear out including many rubber items. (brake lines, drive shaft couplers, suspension joints) MEchanical parts are plentiful but interior parts are scarce.

Cracked under body undercoat is a pathway for rust to get behind. I generally peel off anything loose to keep water from sitting.