On March 11, 2000, about 1400 hours Pacific standard time, a Robinson R22B, N7078B, impacted the window of a commercial building in San Diego, California, during an attempted takeoff from a parking lot. The helicopter, operated by Smiley's Helicopters, Oceanside, California, and rented by the pilot, sustained substantial damage. The private pilot and nonrated passenger were not injured. The personal flight, conducted under the provisions of 14 CFR Part 91, was originating at the time of the accident with a planned destination of Oceanside. Visual meteorological conditions prevailed and no flight plan was filed. Federal Aviation Administration (FAA) inspectors from the San Diego Flight Standards District Office examined the accident site and interviewed the pilot. In a statement to the FAA, the pilot reported that he had landed the helicopter in the parking lot where his business was located in order to drop off his passenger and to complete some business. The parking lot on the south side of the building was empty and he flew an approach to the parking lot from east to west and landed. He then shutdown the helicopter and went into his office. The pilot stated that he had a different passenger for the return trip. The pilot elected to takeoff in a northerly direction along the west side of the building. The north end of the parking lot was empty, except for a van parked at the end. The FAA inspector stated this placed the pilot in a position from which he would not have a clear, unobstructed takeoff path, effectively eliminating his ability to remain in ground effect until entering translational lift. The pilot lifted to a hover, took off, and started his departure to the north. About 50 feet along the takeoff path, at an altitude of approximately 16 feet agl, the pilot noted the rotor rpm was low due to the sound of the low rotor rpm warning horn, and elected to execute a forced landing in the parking lot. As he set the helicopter down in the parking lot he veered to the right to avoid hitting the van, and the helicopter came to rest facing in a westerly direction. The tail rotor contacted the office window closest to the helicopter, breaking the window, destroying the tail rotor, and damaging the 90-degree tail rotor gearbox. The operator did not provide a pilot/operator accident report on NTSB Form 6120.1/2.