On December 12, 2002, about 1630 Pacific standard time, a Piper PA-12, N87800, collided with terrain following a loss of control while maneuvering near Fallon, Nevada. The owner was operating the airplane under the provisions of 14 CFR Part 91 for the local area flight. The pilot was demonstrating the borrowed airplane for a prospective buyer. The pilot and passenger were not injured; the airplane sustained substantial damage. Day visual meteorological conditions prevailed, and no flight plan had been filed for the personal flight that departed Fallon Municipal Airport about 1600. In a written statement submitted by the pilot, he stated that the prospective buyer requested the pilot fly for the demonstration. The flight departed Fallon Municipal with the pilot in the front seat and the prospective buyer in the rear seat. The pilot was demonstrating an approach to land with the prospective buyer following on the controls. During a turn to a simulated "final," the prospective buyer inadvertently applied left rudder. The pilot applied right aileron to correct; however, the airplane entered a slip and then impacted the ground. The pilot recommended better instruction to passengers to prevent future accidents. The pilot also reported having about 100 hours flight time in the make and model of the accident airplane with about 2,900 hours total time. The Federal Aviation Administration (FAA) inspector completed a post accident examination. Continuity was established for all flight controls.