...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.
I do not intend to sail alone. I have a friend who is a mechanical engineer and has some experience
...a large catamaran is probably one of the worst boats to learn to sail on, and this is coming from a multihull sailor.
I intend to take classes and will not jump in bluewater immediately.
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....
You are right, I don't have that experience but I will give a try and I really don't think you need a PhD to learn the basic and the principles.
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 don't know anything about prices and maintanance.