If you keep it in the water year-round (which you obviously would as a live-aboard) and only haul it periodically to check and do routine maintenance on the hull, and if you’re comfortable doing woodwork and maintenance that your life will depend upon, then it may not be such a bad idea. Letting the hull dry out, say over a winter season, for example, means that the hull will be leaky when you first launch it in the spring – and I mean quite leaky, so living aboard soon after first launch could be problematic.
The response would be different for a boat kept in tropical waters, instead of the temperate waters of Northern California. Worms in tropical and subtropical waters can eat up a wooden boat.
Have the thing professionally surveyed, since you’re obviously new to this, and pump the surveyor for the answers to these kinds of questions.
Cost is going to be dependent upon size and the current condition, whether you plan to do “restoration” work to make it a showboat, or just a serviceable home. Then if you plan to take it offshore, engine maintenance is another big issue.