Just an extra bit to add in -
If you can't have roosters, I would say don't look for "dual purpose" then. The whole point of DP birds is a self sustaining flock that you can continue to breed. Otherwise, having some layer hens, then processing them when they're done laying. . . Well that's just what a lot of people do anyway. It's not really dual purpose, because even the Barred Rocks from a hatchery will give the same amount of meat as the Polish from a hatchery. And speaking in the origin of the breed, Polish don't lay much, and aren't dual purpose. Barred Rocks lay decent, and are dual purpose. But from a hatchery, you get the same - little to moderate meat, good laying abilities.
I'm certainly not meaning to pound on anyone for wanting hatchery birds, I'm just making a point. . . . You can't have a truly dual purpose flock from hatchery quality stock. Hatcheries don't and never really did breed for that. . . . They breed for "pet" chickens; hens that lay a bunch and then are done within 2-3 years so you keep going back to the hatchery.