I think the only thing we've paid for is the chicken wire. We just put them in the barn stall that opened out into an enclosed run. The person we bought the house from was a contractor and left a shed full of tounge-in-groove 2x6 beams that we use for everything. My husband can mill that wood into whatever size he needs it seems and built the nest boxed out of it. I just don't see the point in paying for things that you quite often can get if you just look around and work at it a bit.
