I live in Tampa, and could tell you that just finding a marina with available slips is hard (let alone liveaboard). All the marinas doentown have 5-10 year wait lists. Ant they are EXPENSIVE. Try you might have better luck over in Pinellas County. Also, post on craigslist (or similar). When I was looking for a place to keep my boat I found there were a lot of people who live on lagoons that have open dock space. With the economy how it is, people are looking for any way possible to bring in extra $$, so might be more willing to let you live behind their house.