Re: A bluewater live-aboard for under $20k
You might consider a Pearson Vanguard. Great first boat. Good headroom, solid hull, ok sailor. Also, easy to singlehand conservative rig. Watch for core issues on deck, but relatively simple to repair. Dinette layout is great dockside for live aboard. 6-10K would get you a good start, probably with a diese, though parts for the A4 are abundant and a simpler engine was never designed.
I've been aboard full time for years and find her pretty comfortable. At 10 K you'd have money left over for newer sails, a reefer, upgraded electronics if desired, dodger etc.
The boat is plain inside, but think of it as a blank canvas since your a good woodworker.
One big plus is relatively shallow draft so you can poke your way down the coast. Many have voyaged far.