What happened
While approaching the airport, the pilot shut down the left engine of the aircraft to demonstrate a single-engine landing procedure to a prospective new owner. As the aircraft transitioned from the base leg to final approach, the pilot in command attempted to extend the landing gear, but the mechanism failed to respond.
Upon realizing that the hydraulic pump was driven by the left engine, the pilot decided to attempt an engine restart. Before initiating this procedure, the pilot transferred control of the aircraft to a passenger. Although this passenger held a commercial rating, they had no prior experience flying this specific make and model of airplane. The attempt to restart the left engine was unsuccessful.
After regaining control of the aircraft from the passenger, the pilot determined that the aircraft had overflown the airport. Consequently, the pilot elected to perform an emergency landing in a nearby wheatfield. During the course of the landing roll, the aircraft struck a fence.