I grew up in Seattle, so I was familiar with floating homes before I ever saw Sleepless in Seattle. These fun waterfront (water-top, I guess is more accurate) homes can be great if you don't mind replacing yards and grass with a lake or river. Of course, they're not practical everywhere, but if you live in one of the areas where floating home communities are popular, they can be a fun condo alternative. They can also make for great recreational or vacation properties (I'm sure you'd have no trouble renting out such a unique vacation home either)
And if you like the rustic look, you can now find builders who will create floating log cabins with all the comforts of a land-based home.
As one company writes, "A Floating Cabin is designed to provide recreational housing on the water. Built on an aluminum frame with encapsulated, foam-filled floatation, the Floating Cabin adheres to all U.S. Coast Guard rules and regulations. In essence, the Floating Cabin is a houseboat with a hull ID number that can be equipped with a motor or transom for relocation. Most units are shipped to marinas to be used as overnight accommodations or as water condominium investment properties. Additionally, individuals purchase the Floating Cabin as investment opportunities or to rest at the end of their dock on lake-front property."
Prices start around $50,000 at http://floatinglogcabins.com/