Let me ask this: Why do you want chickens? If this is how you want to keep them, it will be considerably cheaper to just buy the commercial farming eggs from the store and you will get the same product in the end. You will not have to care for the animals either, which takes time and money. Having chickens is more expensive than buying them from the store. Most people get chickens because they want healthier food for themselves and their families. Allowing the birds to free range on your pasture is better for the chickens. They consume a lot less feed, which is expensive these days. They then produce much better eggs, with an orange yolk instead of the pale anemic yolks from store bought eggs. The dark yolk color is directly related to the amount of beta carotene in their diet. (dark leafy greens are high in beta carotene) Look around this site and you will see numerous photo comparisons between eggs from hens that forage and those from the store. There really is a HUGE difference in looks, taste and texture. I myself will never again eat store bought eggs. Overcrowding can lead to many problems, such as feather picking, egg eating, severe wounds and cannabalism. Once these problems start, they are very difficult to stop. As others have stated, if you can build those sheep shelters, you can build a coop. There are a lot of ideas here from people that have built coops from completely recycled materials and are still appealing to look at. If you REALLY want birds to raise in a small confined space, I would strongly suggest you look into raising quail. They are much more adapted to a small space, and they lay eggs roughly 6 weeks from hatch.