Model sailboats often operate with the same sophistication of design as any full-sized yacht. The more sophisticated ones are designed for racing, and the R/C sailors call them "model yachts", to distinguish their more sophisticated models from the "toy" sailboats often sold at toy stores or online. The "model yachts" sailed in competition are generally better-quality, more rugged, and more costly than "toy" sailboats. They use readily-available parts (from hobby shops), so you can repair the yachts when something goes wrong. Often, "toy" sailboats require an overseas order to get replacement parts. As with any hobby-sport, the cost of the model yacht reflects its degree of sophistication. The "model yacht" market is supplied by a number of highly qualified one-man companies as well as by a handful of larger companies. The "toy" market is generally served by larger toy companies. The long-term cost of model yachting is far less than the cost of sports fishing and golf. The start-up cost depends on the model sailors willingness and ability to build his/her own boat (from a kit or scratch), as well as the sophistication of the yacht itself. You can expect to invest as little as $450 and as much as $5,000 for a true "model yacht". After obtaining the boat and related gear, the actual cost of sailing is very low.

Summary:
Learn as much as you can about the types of a model sailboat. Expect complexity. Be prepared to spend some money.