I tried to sell a car a few years ago, try not to set your expectations on what you see them advertised for as this is not the price they will sell for and you will be disappointed (i know i was)! I would stick to the valuation on car sales, and maybe add an extra grand on top for negotiating purposes. When someone is looking at a buying a second hand car places like car sales valuations is one of the first places they will look to see if they are being ripped off and if you are too high above it they won't be interested.

Good luck! I hope you get to buy your house!