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.