A while back another fellow was asking about a similar dream, and I left a lengthy comment there regarding my decision and experiences living aboard a 30' pre-loved boat. You can see it here:
A green sailor!
In general I say go for it, but cheap old me says don't go into hock for anything greater than $20K unless you're making a serious commitment to the lifestyle and/or win the scratch-it lotto. Also, I personally find 30' to be the height of comfort. There are a ton of good old boats out there for reasonable prices (i.e., the combined parts are probably worth more than the total asking price), and you can always trade up later. You'd do well to just start touring the different boats on the market and researching their characteristics as you go.
Job #1 though is to figure out how tough it is to get liveaboard moorage at a marina where you want to live.