The repair cost for a vehicle includes all the parts you buy while that car is in your Workshop, even if those parts are never put on the car. This can make it seem like you're losing a lot of money when you sell the car, but you've still got those extra parts so don't sweat it.

To make the most money buying and selling cars, try to buy cars that have a good number of parts. Repairing parts is easy (hey, you're a mechanic) and cheap, but buying new parts can be expensive.

Shop at the Junkyard! You should always check the Junkyard for parts before going to the catalog.

A good strategy is to always buy top condition parts if you see them in the Junkyard. If you don't, someone else may come along and snatch it when you need it. You can save a ton of money this way.

With the Service Pack 1 Update applied, the Junkyard can fix up those totally busted parts. If you've got a black part, scrap it. Then you can go to the Junkyard and find that part on the shelf; only now it will be in red condition, which you can repair.

You can't see the entire car, but you can see what the other bidders are doing to get an idea of what a particular car is worth.

Don't start bidding right away. See how badly everybody else wants the car.

Placing bids will drive up the price of whatever car is on the block.

The other bidders at the auction like to see custom parts.

The other bidders especially like to see completely assembled regions. If you do nothing else when you fix up your cars, put all the parts there!

If your car is on the block, and it looks like you may lose a lot of money, you can outbid everybody else. If you win it, you'll only have to pay a fraction of your bid to get your car back. It may end up saving you some money.