So... you don't have them yet. Good. Do you have the coop built? If not, I would suggest you build it bigger than you think you need. Especially if you plan on hatching chicks. It is VERY important to have a plan for any chicks you hatch. Will you have room to expand your flock? As stated previously, it can be a disaster if they are over crowded. What is your plan for the extra males you will end up with if you hatch? It's really not the best idea to keep them all together with the established rooster and hens. As also previously stated, they will gang up on the females, continually harassing and gang breeding them to the point where they may not be able to eat, drink or dust bathe in peace. (This is the voice of experience speaking. That situation didn't last long.) It's not the best management to cause your hens/pullets that kind of stress. That can also affect their laying. I wish you the best with your new hobby. Chickens can be a lot of fun, but if not managed properly, chicken keeping can also be heartbreaking.