The airplane had received an oil change prior to the accident flight. The pilot stated he performed an uneventful preflight inspection of the airplane and prepared for departure. During his taxi to the active runway, the pilot stated he did not notice anything unusual about the oil pressure and temperature indications. The pilot said the takeoff was uneventful and shortly after leveling off from initial climb, he experienced engine vibration which became progressively worse. The pilot declared an emergency with air traffic control and requested vectoring back to the departure airport. Eventually, while over a residential area, the airplane's engine seized while heading back to the airport. The pilot selected an open field within the area of homes. Believing the emergency landing field was attainable, the pilot extended the landing gear. Shortly after this, the airplane struck a single family home and came to rest on the home's roof and side. The on scene investigation revealed the airplane's propeller oil return line had disconnected from the engine's crankcase fitting. An examination of the airplane's taxi route revealed a trail of oil from its parking place to the point where the airplane began its takeoff roll.