It started with just a small 5' x 5' x 8' timber framed play house which was free! Concreted the posts in the ground, some extra lumber I had laying around from when I have built other things, extra OSB and siding from my house, and some extras from Home Depot. Heck I didn't even buy the shingles they were extra from my house too.
My biggest expense was to buy the fencing, hardware, and the chicken feeder and waterer.
Oh and the chickens.I have 6 RIR's and 2 black sex links. When I got them they were about two months old so the little lean-too off the side is 4 nesting boxes that I can access from outside the coop. Yay! No poop on your feet to get eggs.
