There is a web site which has masses of advice & info on the ins & outs of living on boats. All sorts of legal advice & serious stuff. Can't remember now where I found it, but I'll have a hunt about - it can't have been that hard to find. It sounds like a lovely thing to do, and everyone I've ever met who has done it has loved it. I suppose I'm half-way there though - we've got 1.5 foot of flood water under our floorboards, so we are technically living on the river!!
Best of luck in evangelising to the madame....

Kris