Here is a simple toy car you can build for very little money if not none. These cars are paintable and drivable. The design on this one is just the result of a quick put together, but you can fancy it up as much as you want.
Step 1: The Supplies...
Your gonna need four bottle caps, four tacks, foam, and a way to cut the foam.
Step 2: The Wheels...
First poke a tack through the middle of your bottlecap. Then repete.
tip: you can find the center of your bottlecap by lookin for the tiny little bulge in the middle of the cap.
Step 3: The Last Part Is the Assembly.
It's pretty obvious what to do here.