There is a gentleman called Paul Smith who has an interesting story to tell. His is a story about learning all things narrowboating, and it was, I can assure you, the hardest way to become a liveaboard. (I read his book)
He is in the process of producing a calculator that takes all sorts of info that is needed, or not, to generate a cost and budget for living afloat.
I opted to be one of the testers so have given my initial feedback along with others who are fine tuning the application.
Follow this link to get access to Paul's site ....this link
It is worthy of success.