As others have said, hens will lay anyway. If you get one that becomes broody, she wants to hatch chicks. You'll need to keep an eye on her - a friend's bantam starved herself to death sitting on a hidden clutch, easiest to let her hatch a couple and keep, give away, sell or eat.
I bought 'sexed' chicks, but one turned into a very handsome cockerel. I hung on to him and didn't think twice about not eating the eggs, just collected them every day. A neighbour fed and collected when I was away.
If you let them out 'free range' in your garden - you won't have many plants left. So either protect plants or limit the range of the hens.
Warning, if you fancy bantams - they fly and will escape, so you will need to clip one wing's feathers regularly. It doesn't hurt them.