Sail vs. Power
I hate to say it, but if you you know nothing about boats starting off cold with a 50 footer is not going to be easy. I seriously suggest you sign up for lessons with a sailing school finish their program then charter a few boats. You will save a big pile of money and learn a lot in the process. One simply does not learn to sail on a 50 foot boat. Same for a 50 foor power boat, you will need to hire a captain unless you have the experiance yourself.
How to decide power vs. sail:
1) Power boaters always want to get there fast so they can shut down that damn noisy engine. Sailors can''t be in a hurry to be someplace. So, do you want to enjoy the sail or just get there?
2) If you want to cross an ocean, sail is the only way. Small power boat just don''t have the range