I'd suggest you get their vaccination history. If they have been vaccinated against Infectious Laryngotracheitis they are carriers and will infect any chicken they come into contact with in the future unless the new chickens are also vaccinated for this. It's not a reason to not get them, just something to be aware of. I'm no saying all commercial hens are vaccinated for this, just that it is worth knowing if they are.
Best of luck in this endeavor.