the building inspector is a good first stop to make. I'll add to Emmett's post that surveying an old barn can be a tough job even for an experienced framer. untill dismantling you won't really see the condition of the all the timbers, especially the main floor timbers. You are right to have reservations.... in my opinion, moving an old frame requires time, patience and money, not neccessarily in that order(money will probably be 1st). BUT they are beautiful, inspiring, and often stronger due to use of old growth trees.