I lived aboard a San Juan 24 for two years while a student at SFU in the early 80's. Worked out OK although I would have liked to have been able to stand up in the boat. Costs go way up dramatically with the size of boat not just because it has more gear. Haul outs, paint, moorage and other things. Currently have a Yamaha 33 and my family and I cruise on her in the summer through the Gulf Islands and up to Desolation Sound. I think that you could find a pretty nice boat for under $50K which you and your girlfriend could live on. I have spoken to the owner of the Union Steamship Company Marina on Bowen and he has some legal liveaboard spaces. Its the number of people he has approval for, not the size of boat. There is a per head surcharge for living aboard there. If you can find an older French boat with three cabins I think you'll be OK.