House Boats on Lake Union
House boats nowadays are selling for around $300k to $350k. Check out these house boats currently for sale. You'll also be able to see how they look inside. :) First. Second.
This is Bill Gates' house. It's located east of Seattle across Lake Washington in a city called Medina. His 11,500 sq ft house sits on 5 acres of land. The house doesn't look big in the picture. That's because it's covered by trees and I didn't shoot the entire house. Yes, his property extends to the left and right of the picture. :)
For more details on Bill Gates' home, check this article from US News.