At 102 in (259 cm), the G650ER has the widest cabin yet but should be joined by the Falcon 5X (a Global 5000/G500 competitor) and its replacement, and the 4,500 nmi (8,300 km) Citation Hemisphere in 2021; at 98 in (249 cm), the Global 7000/8000 is wider than the 95 in (241 cm) Global 5000/6000, the same as the Gulfstream G500/G600 and the Canadair Challenger, while the Dassault Falcon 8X is 92 in (234 cm) wide and the G450/G550 88 in (224 cm).
In the United States, business aircraft may be operated under either FAR 91 as private operations for the business purposes of the owner, or under FAR 135 as commercial operations for the business purposes of a third party. One common arrangement for operational flexibility purposes is for the aircraft's owner to operate the aircraft under FAR 91 when needed for its own purposes, and to allow a third-party charter-manager to operate it under FAR 135 when the aircraft is needed for the business purposes of third parties (such as for other entities within the corporate group of the aircraft's owner).
You will be told how much the hold can take on your chosen aircraft and can upgrade if you feel more space is needed. This will generally be far more than that of a commercial airline. You may also need to upgrade if carrying things like golf clubs and skis. If travelling with a gun, you will need to provide a license and the gun and ammunition must be kept separate. It is then at the captain’s discretion whether it can be on board.
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.