I agree with what dog and Jeff posted. Keep in mind that what works well racing or hopping the gulf stream will not necessarily work well loaded with the gear and supplies needed for a longer passage - say 2000 lbs+.
As far as build vs buy there will be a vast difference in price. An older boat will come with a diesel (new 10k), rig and sails (10k to 20k), as well as probably 20k+ in other equipment if purchased new. The hull and deck is probably less than 40% of the cost of a complete boat. Dog posted a link to James Baldwin's site - the entire site is worth a good read. James Baldwin has gone around twice in his 28' Triton and has a business consulting and modifying boats for offshore voyaging. Atom Voyages | About the Sailboat Atom
I think the Vagabond would be a good coastal cruiser but not a good choice for offshore voyaging.