I too was surprised to read the word "minimalist" in the same post as 50 foot boat!
I think the short answer for how much it is going to cost is that it is going to cost you the same thing it costs you right now, plus and minus a few things. Getting on a boat doesn't suddenly change your life, you bring your life with you, same life, different location. If you're used to eating fresh pineapple every day, you're going to want fresh pineapple every day. If you live a big life now, you'll be living a big life on the boat too, at least until you change it. It's amazing how many people seem to think they are going to wash clothing at the laundromat, ride bicycles to the store, bake bread from scratch, etc, who wouldn't DREAM of doing that right now