If this boat is really destined to be your boat and used by you after charter - design it with that in mind - it will generate charter income if managed correctly and marketed to the sailors that will appreciate it. 3 heads on a modern boat is plenty - a crew cabin is an unusual configuration for personal use down the road but sure helpful if you expect bareboat charters to be hiring a Captain for the week - try and establish a good relationship with a local Captain who can do most of your work and the boat will benefit as will you and the guests.
Buy A Boat!! Sail it !!