If I was purchasing a J/30, I would look for a J/30 in good rig and engine. The bottom is something you redo every 6 years. Take a look at Blitz. This information is available on page http://www.j30.org/html/market/boats.html

Blitz recently won the 2003 North American Championship in Annapolis with a bunch of wankers on board. The boat needs a new bottom, but otherwise in good shape.

If you live on the coast and need a new bottom, I recommend taking the J/30 to Diversified Marine (aka Donnie "MojoMan" Brennan).