budget $100/ft. /month.
So, for a 50 footer, figure $5000.00/month.
It will likely be less, but budget $5000.00 to play it safe. If it is less please forward the excess to me as a management fee.
BTW, "modest tastes", "minimalist", and "45-50 footer " and "steady stream of guests" do not dovetail together. Simply because of it's bloody size, a 50 ft' boat precludes minimalism. It is damn hard to live like Thoreau when you are on a Trump-sized boat.