I am good friends with all the big box stores and all the small hardware stores in town. I go at least once a day to pick things up. When people say they use scavenged or recycled items, I wonder if they have been collecting things for years or if they have a huge garage that they can rummage through to find what they need. Sure I'm going to be furnishing the place with used furniture and dishes because I can do that over time, and the local 2nd hand stores have a lot of items to choose from.
Aside from Habitat for Humanity's Restore where do I find "on-demand" building supplies? Craig's list has been a total bust for me. Again, if I'd been gathering things over the last few years, I'd be good. Alas I didn't.