All through my childhood, my parents had a floating Boathouse, for weekend use, but the boathouses on the Columbia River, were very different from the houseboat shown in Doberman's pic. The houseboat shown in Doberman's pic was much more mobile, even though not self propelled. Rather than having a barge style hull, the boathouse's in our moorage were built on a float of LARGE logs with lumber stringers forming the foundation of the flooring, with standard stick built framing and either metal siding or lap siding. The boathouses were connected to full electrical, water and sewer connections, as well as phone and later cable TV. they were semi-permanently moored, and it was rather a production using small tugboats on the rare occasion that one was moved.
like most, our's had a "Boat Well" with rolling doors where we kept our boat. who, built the first is unknown, but it assumed that the original was simply a covered floating boat dock that someone added a bed, kitchen and bath to, and the idea evolved, and they became more refined over the years. Our boathouse was a simple but comfortable one with a large living room, small kitchen and bathroom, with two small bedrooms. with several dozen boathouses in the moorage, it was like another neighborhood, where many Families became close Friends and often vacationed together. It was an AWESOME childhood, that I wouldn't trade with todays kids for anything. Unfortunately my Father sold the place about 20 years ago, and several years later, the house was destroyed by a fire, so ended an unlikely dream of ever buying the Family place again.
I don't have any digital pics of our old place, but if I get a chance to take some pics of some similar Boathouses, I will post them for others to see. While our's was modest, there are many now days that sell in $250,000+ price range, and are as nice as any home built ashore.
Doug