I will give the advice to stick with just hens the first year or even two. There is a learning curve to chickens and their behavior. If you have children under the age of 5, I strongly recommend that you not get a rooster. Roosters have ruined the whole chicken experience for a lot of kids. Kids are who roosters generally attack first.
People always have roosters to give away, your friend will have some more next year. An all hen flock is a much more friendly flock, and will look to you to be the leader. You will bring them feed, and they see that as a good thing.
A small flock of hens can easily be over mated by a roo. Your flock sounds like it might be quite young, and therefore smaller, what often looks like enough space or even a lot of space, rapidly gets too small as the birds get bigger. See how the group you have now settles down in the space you have.
And the biggest reality with roosters is that some are fantastic and some are nightmares. Human treatment that will produce a well loved puppy, often times creates a monster for a rooster. Roosters often regard affection as submission, and will attack to get he upper hand. If you do not think you can cull a rooster, you probably need to wait to get one.
I had hens for 4 years before I got a rooster. I love having a rooster now, but I am glad I waited. I learned a lot in the beginning.
Mrs K