In the past (when we were a bit younger), we thought it would be a great combination to get a smaller houseboat to use as a camper, to be able to use it as a conventional camper in a campground and then be able to launch it on a body of water any time we wanted, having the best of both worlds.
Well, we never ventured that direction and only pipe-dreamed about the possibilities. But the thought has been there for years and years now.
We have, on many occasions, seen at different Indiana State Recreation Areas (like State Parks) where folks bring their boats (of all sorts), will pitch a tent to hold their campsite, and then take their boats on the water. When the return at the end of the day, the end up sleeping in and using the boat for night time shelter. Usually, the smaller kids end up in the tents.
What I'm saying is, it's not such an crazy or an unusual idea, as many folks are already doing what you are thinking. I think if you could find some boat forums and check them out, you'll find out that a lot more people than you imagine use their boat as a camper on land and a boat as a boat on water.
If you have ONLY the funds for one, and really want to enjoy both worlds, then a smaller house boat on a towable trailer is the way to go. It might be awkward sleeping in a conventional speed boat, or a Bass fishermans's boat at a Cracker Barrel overnight! But you probably would have no problems with a towable house boat.
