My first attempt at letting a broody hen hatch eggs didn't go well due to my lack of knowledge. We got one chick out of it and she's laying now, so that's a great feeling. Unfortunately, I didn't do enough reading beforehand, so I didn't learn about collecting eggs ahead of time and starting several under the hen at the same time so you get the same hatch date. I also didn't have the hens with the rooster long enough before starting so we had a lot of infertile eggs.
We left momma with her chick for a couple weeks before separating them, but we had the two of them separate from the other chickens for safety's sake. When we were about a week from what we thought would be hatch time, we very carefully moved the hen, nest and all, to a separate pen. Her nest was made inside a plastic bin turned on its side, so we were able to just pick up the whole thing and move it.
We ended up buying a few chicks that were about 10 days younger, so we put our hatchling in with them; my husband tried to put one of the new chicks in with the hen and hatchling, but she attacked it instantly [hubby immediately had one of those "should have listened to my wife" moments!]. We do want our chickens to be friendly and comfortable being handled, and now I've read that not leaving them with momma is better for that.
I would just advise you to do lots of reading about it before you get started, so you can get the most possible eggs to hatch. Good luck!
