We vacationed on a rental houseboat with three other couples on Lake Cumberland in Kentucky. It was a good time. BUT....
We used a lot of fuel for both the boat motor and the diesel generator. Cumberland, like many lakes in that region, is an impoundment with very steep, rocky banks and few level places to get off the boat, so you're on board for the duration. Our rental was 65' long and 15' wide. We saw privately owned boats that were floating palaces, up to 100' long and with three decks. A trailerable boat is of course much smaller and more restrictive.
Bottom line, it was fun, but it seemed like it would get tedious after a while. And no way is it cheaper than RVing.