Another important factor Fazal-Karim suggests considering is the length of time you plan to own a plane. He says the average period of ownership is one decade, and typical depreciation in aircraft value drops about 10 percent to 15 percent in the first year with a further 10 percent each subsequent year. Due to low inventory and high demand for pre-owned aircraft, the Jetcraft Market Forecast predicts depreciation rates will improve over the next 10 years. Jetcraft
Though the early Lockheed Jetstar had four, most production business jets have two jet engines, mostly rear-mounted podded engine. If mounted below their low wing, it wouldn't allow sufficient engine clearance without a too long landing gear. The HondaJet is the exception with its over the wing engine pods. Dassault Falcon still builds three-engine models derived from the Falcon 50, and the very light jet market has seen several single-engine design concepts and the introduction of the Cirrus Vision SF50 in 2016.