Whatever you do please dont buy from a poultry farm.
I'm not sure I agree with this. I bought 4 pullets ($17 each) yesterday from an egg farm in outer Melbourne, where they were in a huge shed, two to a cage. I chose one bird from each cage to let the remaining pullet stretch her wings for a while. At the back of the shed were long rows of 'older hens' (18-24months) for $4 each. These were ex-layers/ex-battery hens to be sold off or presumably headed for the pet food factory shortly.
I considered taking two young hens and two older, but thought they mightn't get along in my small coop. Most people seem to approve of getting ex-battery hens rescued by or given to an animal welfare agency, but what's the problem in getting them directly from the poultry farm, cutting out the middleman and saving them the shock of resettling twice? Those older hens all deserve a second chance and I'll probably increase my coop size to get a few in the future.