Lots of boys build model car kits as kids, and as a result, many adults become avid collectors of the kits as an adult. Many also spend lots of money working to preserve their childhood pastime! Some of the original kits - some from the 1960s, like the original Batmobile kit or the Futura concept car - now go for big bucks on eBay, other collector sites, or through antique dealers.
The kits come with all the parts needed to make the car, and sometimes come as a blank canvas and the builder, once the kit is assembled, paints and finishes the car. Model truck and car kits come in a variety of materials, including metal, plastic, and resin, among others. All types of cars are available in model car kits, whether it's a classic car or truck, a service vehicle, a roadster, or some other type of specialty vehicle, like a semi truck or a construction vehicle.
Many car kits come in pieces, and users have to purchase different parts separately. This sort of "custom building" is mostly what professional collectors and builders are into, and it takes a much higher level of knowledge and craftsmanship than it does for a beginning builder to create a car from a pre-assembled kit. When builders make a custom kit from scratch, they often purchase decals, paint, and other specialty items; some builders even get as detailed as purchasing real chrome and other high-end materials to finish the car or truck.