I think you need something to cook on. That is why most boats give you those little propane stoves. And a place to sleep(cabin)The boat does not need running water,or a potty . I could be wrong though.It might need the potty. I remember an article on it a while back ,if I find out I will copy it and post it. But I think it's only those 2 things.
Best thing to do if you can is take out a home equity loan and buy a boat with the money. Then you can automatically deduct the intrest,and don't have to worry about the 2nd home thing.