I stumbled across an extensive website by Bill Dietrich on his research for retiring onto a sailboat. Bill has compiled a lot of information, all of which makes for thought-provoking reading. [As an aside, from reading all the feedback and assistance Bill captures in his pages, I agree with the premise that if you ask 10 sailors, you will get at least 15 different opinions.]
Anyway, there is a section in there on boat buying which you may find helpful. Good luck.