If you're looking for used (but good condition) building materials for your natural home build, contact
local hotels and resorts. They will VERY often upgrade rooms, and get rid of perfectly good doors, windows, trim, furniture, cabinets, small appliances, etc.
I was contacted by one local resort manager who had heard that we were looking to recycle building materials, and we were able to get eight interior doors, a 60" french glass door, two exterior steel doors with frame, handles, and locks, an apartment sized fridge, a microwave, six kitchen chairs, two futons with mattresses, 8 large slider windows, and 4 smaller casement windows. Do you know what we spent on that?
ZERO. Nothing. Nada. Zilch.
All because I put the word out.
Heck, they even had huge jacuzzi tubs that they were giving away. And lots more that we just couldn't use.
So, if you need something, put the word out! It's amazing what people are willing to part with!
(I also got four Anderson casement windows for free from a neighbor.)