When our local shelter has bunnies, if they are to be euthanized, they call me and I go get them for free. I would ask who had the chickens, most likely someone got them for the kids then didn't want them once they grew up and were noisy. They would be hatchery birds that lived isolated from other chickens. They would be fine then, but it still makes me nervous about Biosecurity, so quarantine for sure. They should be cheap or even free if it's a well run place.