Any 2nd hand cars please get a reputable Subaru mechanic to check & advice before purchasing it.
If the previous owner is good, the previous weakness like rear wheel bearing fast wear out can be fixed with updated backing plate.
The rest are normal wear & tear like replacing lower arm bush, leaking top valve cover gasket, re-RTV timing chain cover, radiator & rubber hose service/replacement.

Worse scenario, flood or accident car. (Need good experience mechanic to check)
Gearbox body valve (solenoid) issue, engine overheated before, high engine oil consumption, coolant mix with oil, fail modify project from previous owner (this really headache if not done well by previous mechanic) All these issue cost a lot of $$$ to fix and some owners might just give up and quickly sell in market. Usually a good, experience mechanic can pinpoint it and advise you to avoid.