Quit to sail
It depends on where you go around the world. To go around Cape Horn, I would recommend a minimum 40 foot deep draft fixed keel (no centerboard here. She will snap one like a twig. ) Cost of ownership varies. Before buying, enlist the services of a professional surveyor unless you are buying new. Get at least a year of sea time in to make sure you can handle it. The sea is littered with inexperienced wannabes who got in over their head.