One of the more rewarding aspects of the potting shed project was using some reclaimed material. The three windows came from our neighbors across the street. They were redoing their sun patio, and Gary happened to see this and asked what they would do with the old windows. Since they were just going to trash them, we ended up stashing them away for about 3 or 4 years in hopes we could use them. We finally did.
The doors came from "rebuilders center". Not as cheap as the free windows but worthwhile.