I once bought a very cheap statesman off a wrecker . I cleaned it up and did a few jobs then advertised it added $6000 from memory
I had buyers coming out of the woodwork
just thought they must be in demand
First buyer bought it on the spot
A few months later I dropped by the wreckers where I'd bought the car .
Was told we made a bit of a mistake on the sell price

So both the buyer and myself got a good deal