I can give you some advice. If the barn is in poor condition, from what you write it sounds like it is you are going to get few good pieces. Maybe a few collar ties, posts and pins. Don't count on salvaging most of it because it will not happen, unless the barn is in mediocre to good condition. A few years (8) This Old House (after bob) did a show on rebuilding a barn in Concord, MA. $250,000 to tear down and rebuild, from foundation to shingles. That's not including all the donated materials, and labor. Besides the point, they used a timber framer by the name of Ted Benson. He owns a large P&B company in NH. Do some research, try to track the company down.