You better buy a boat that is already in a slip in San Diego, and get the rights to the slip with it. That is if market conditions are the same or worse (or better depending on your perspective) than when I was looking several years ago.
If you're young and single I say GO FOR IT, you'll never regret it.
Assuming you're not going to buy a Wally or other ridiculously expensive boat, get something like this:
http://www.searay.com/2007_sea_ray_s..._sundancer.asp
and get a slip at the Marriott Marina in downtown San Diego. All the amenities you could want including "dock" food service and a gym (think: shower bigger than a shoebox).
And keep us posted so I can live out one of my regrets vicariously through you.
P.S.: Be prepared for a ****load of maintenance, but IMO its well worth it