Bought my 1969 Camaro at auction three years ago. Paid too much, didn't do enough due diligence, and spent the first six months dealing with problems I should have caught before I bid.

The engine had been rebuilt with mismatched parts. The brake system had a dangerous combination of old and new components that shouldn't have been mixed. The floors had been Bondo'd over rust rather than properly repaired.

Four expensive lessons: always get a pre-purchase inspection, always do a test drive if possible, always pull a carpet corner, always ask why the car is being sold. I know all of this now. Wish I'd known it then.