Caveat Emptor
Let the buyer beware. I never saw a "rent to own" option in the north either, however it is common in the south. In my experience, most of those "deals" are boats that have either been sunk, been abandoned at a marina or generally have other serious issues. Frequently there are liens against them.
You should NEVER purchase a boat without first having a Marine Survey done by a licensed Marine Surveyor, especially if it's a boat big enough to live on. Likely any marina you want to dock at is going to require insurance, and the insurance company will require a survey.
Many people think it's a cheap way to live, I can ASSURE you it is NOT. I don't mean to be discouraging, living aboard can be phenomenal, but it can also be tough.
Good luck.
M/V The 69 Queen
1969 River Queen 40'
and a 24' Pontoon "Red Solo Cup"
Port of Fulton, MS