I second Folly’s thoughts, especially about the disease risk. As someone who was burned big time by the introduction of birds with Marek’s to our flock and the subsequent loss of many beloved chickens, disease prevention and biosecurity have become foremost on my mind.Another option is to buy some straight run chicks of whatever breed(s) you fancy, and raise a few cockerels, and then pick one or two to keep. Your older hens will keep the younglings in line, and it's helpful in raising good boys for the flock. And fun!
I agree that finding an adult will be very possible, and a very good choice, if you are picky and careful.
Mary