Catalina 42 for Blue Water?
Sailing around the world places the kinds of wear and tear on a boat that is the equivilent of decades of normal coastal cruising. The conditions can be very harsh, repair facilities are often widely spaced, and the boats are always heavily loaded placing higher stresses on the boat. A circumnavigation can pretty much wear out a purpose built boat.
Putting a boat into charter can be very tough as well. The boats are used hard by people who are not familiar with that model. Charter boats are out on the water several times the number of hours that a normal cruiser might experience in a year. The Carribean is very hard on a boat and its gear. Charter company maintenance is notoriously underwhelming.Most of the boats that I have been involved with that have been in charter come out really trashed and to one degree or another in need of major restoration.
Of the big three, solely in my opinion, Catalina has generally struck me as the poorest engineered of the three (although Hunter''s current rolled out hull to deck joint does nothing to warm my heart.) One of the big issues with most of the higher production boats is getting access to the hull and underdeck for repairs and to maintain systems. In a boat that you intend to sail around the world, instant access becomes even more critical.
So you are talking about taking an already abused and used hard production cruiser and going around the world. If you were very lucky you might make it but I would never suggest that it is a reasonable way to go. There are a lot of really good distance cruisers out there that are a lot less expensive than the well over $200K that it would take to buy and prepare a Cat 42 for distance voyaging.