Voyage, Seawind, Prout, Leopard, PDQ, Gunboat, Chris White Designs, all make catamarans that would be suitable. The real question is can you handle the boat.
First of all, you've never sailed. That's a huge strike against you.
Second, handling a boat that is 45' or larger takes a fair amount of strength and skill. Are you going to have crew? Sailing a boat that large is going to probably require crew to do so safely, especially given your absolute lack of experience.
Third, a large catamaran is probably one of the worst boats to learn to sail on, and this is coming from a multihull sailor.
Fourth, have you had any boat ownership/maintenance experience? I'm getting the feeling that you haven't. If not, learning the skills that cruising requires may take you quite some time. The average cruising sailor is often his own rigger, plumber, electrician, boatwright, painter, mechanic, etc....
Finally, do you have any clue what the maintenance and ownership costs of a 45'+ catamaran are going to be like? Seriously, finding a marina that will accept such a boat is going to be VERY, VERY expensive. Finding one that is capable of hauling and working on a boat is going to be fairly difficult
I am completly new to this forum and I don't know if this is an old subject, if somone touched it before, but i would like few opinions about a catamaran able to circumnavigate. I'm in late 30s and have saved enough to think about 4-5 years break. I have never sailed and I am ready to take classes and get some experience before going around the world. I want to buy a boat and and cruise the carribean for 1-2 years. My final intention is to circumnavigate and that's why I want a boat able to do it even tough I will first use it localy (around South Florida).
I am interested in a safe catamaran (in rough sea), 45'-50' long, ~$500.000, to be able to rest in normal sea condition, easy to handle.