We recently bought a fairly large coop from Rural King. It is well made, very attractive, and our girls love it.It was a $900 investment that should last us forever.
We combined that with a used 10ft by 10 ft dog pen that we bought from a Craigslist ad. It was $100.
Our total investment is $1000, not counting feeding and watering devices, and chickens.
We have 7 chickens in our flock and they live well in their coop and pen.