When Architect Jim Jessup was a "starving University of Washington student" in 1964, he was able to buy a houseboat on Lake Union in Seattle for $300. He paid $12 monthly moorage, and city sewage hookup wasn't necessary. The houseboats he designs today, on the other hand, cost his clients a minimum of $250,000, usually more; need utility hookups; and often require an additional monthly moorage fee of $300 to $400. In Seattle, where Jessup is still based, most water sites have been developed. A typical houseboat project in that city thus consists of the new owner removing an old houseboat from the site, having the float rebuilt or replaced by a float specialist, and building a completely new home on