Until about 50 years ago, most people would not have thought of throwing away any item which could still be used. Glass jars, cardboard and wooden boxes, paper, furniture, thread, buttons, and re-straightened nails would all have been saved to be used again.
Old buildings are no exception.
I have been involved in the deconstruction of a half a dozen buildings over the past five years. And a summary of the materials recovered from one deconstruction project. Finding the Buildings Word of Mouth Newspaper ads, both yours asking for old buildings to deconstruct and others asking for someone to remove or demolish a building. Chance Assessing the Building - Things to Look For and Test For.