Be suspicious of cars with rust in an area where there are no signs of external damage. The rust had to start somewhere, right? So if it didn’t start on the outside (in a dent or scratch in the paint), then it came through from the back. And if it was bad enough to rust all the way through 18-gauge steel (roughly 1⁄8 inch), there’s a lot more hiding back there. Rust damage doesn’t need to be a deal breaker when you’re deciding whether to buy a car, but be aware of what you’re getting into before committing. See the Metal Work section later in this article on how to deal with rust without spending a mad, crazy fortune.