Most general aviation aircraft are operating under federal aviation regulations part 91, entitled General Operating and Flight Rules. These are non-commercial rules, for people flying for their own purposes, whether that is personal recreation or flying to advance that persons work. Part 91 does not cover people in the business of selling air transportation to others. This means that subject to a few narrow exceptions it is illegal for part 91 operators to sell air transportation. However, many aircraft used under part 91 could also qualify to be used for charter or air taxi flights, operations where the sale of air transportation is allowed. To use your aircraft this way you must have a certificated part 135 charter company operate the plane for these flights, which is a common arrangements that owners often use to earn revenue from their aircraft.