Regarding the cost of materials for a coop, as a couple have mentioned, if you can find some old materials, you don't have to spend a bunch of money. I didn't buy a Single thing for my coop, just used stuff I had around. It's a mobile coop that seats 28, and is way over built. If you just want backyard chickens for an average sized family, with minimal costs, a tractor is the way to go. You can build a simple one of those for very cheap, and probably barely feed them at all. I've got two pullets that are free ranging on a 6000 ft^2 pasture with my goats, I haven't given them grain in weeks but they still give me 2 eggs a day like clockwork.