Any place where water can collect is subject to rust. Water will collect anywhere it can gain access to and not escape. Ultra violet light dries out your rubber seals. On the door, for instance, there's a seal at the bottom of the window sill known as the scraper rubber. This is supposed to squeegee your window dry every time you lower the glass, as well as to prevent water from rolling off your window into the interior of your door. After wind, rain and UV light take their course, this rubber strip dries out, flexes away from the window, and begins to break up. Dirt gets in the door, clogging the drain holes in the bottom, and pretty soon, your door can hold a liter or so of water. The dirt and water slosh around, wearing off the thin layer of paint in there, exposing the sheet metal on the inside of your outer door skin. Hello rust. At the same time this water is being absorbed by your particle-board door panels, which begin to swell and warp. This warpage means the window winder handle scrapes against the vinyl every time the window goes up and down, wearing through that. All the moisture inside the car fogs your windows, stains your headliner, and gets your carpets all mildewy. Meanwhile, the rust has eaten through your door, and is starting to show as paint bubbles on the outside.
This scraper rubber costs $11.95 to replace.
Imagine of the cost of a new door or repair panel (plus welding), paint, a carpet set, a headliner and a new door panel. And this is happening in both doors. You can replace your scraper rubber every two years and still save a ton of money.
The same is true of front trunk or horn boot seals versus replacing the panel underneath the spare tire. And water spraying off the tires will eventually wear away any undercoating in the wheel wells. This water will get into the heater channels under the door sill, and rust it away. Water and dirt that gets in your engine compartment will collect in the well behind the rear wheel, and that will rust away, too.
Good rubber is the key to saving a Karmann Ghia. I can't stress that enough.
f you by a dry state car, replace the rubber sooner rather than later. It very likely will be dried right out when you get the car.
If you're looking at a car from a wet climate, be suspicious of one that appears to be rust free. If the seller claims he recently bought it from a dry state, or restored it, ask for proof. He should have receipts for all the money he spent or a copy of the car's title from when he bought it from California. Never just rely on the seller's say so. It's not at all difficult to hide rust, even extensive damage. Bring a magnet to check for Bondo, and tap on the rocker panels to see if they sound "tinny" (good) or thick (bad). Look for rust bubbles anywhere below the trim line, below the bumpers, around the nose vents and headlights, the gas door, the bottoms of the front and rear glass and the lower rear quarter panels. Rust is almost always worse than it looks, and will always cost more than you think to repair. Collision damage will very often be poorly done and disguised by Bondo, even large smooth sections like the door or fender.