I currently have 7 barred rock chickens. 6 hens and 1 rooster. They have an 8x4x4 coop that holds the nest boxes and roost poles, with an attached run that is 14x8x6. They stay inside the coop/run in the early morning until I let them out to free range and stay outside all day until they go inside to roost at night.
I have 2 Orpingtons and 2 RIRs. We built our own coop. It houses just the 4. It's a hobby for me. Now that doesn't mean I think of them as toys. They are pets and the eggs I am impatiently waiting for are a fringe benifits.
In a perfect world I usually have 12 -15 Chickens; However now I have 10 Golden Comet hens and one Delaware Rooster. I have them housed in a salvaged 4x8 footprint metal shed with 3 levels. I keep them mainly for their manure and also their gardening ability (they prepare the soil for my vine crops when I move the run). Their eggs are a bonus for the table.
Currently we have 20. We have three coops total (only using one now). Normally we have two coops with chickens, one with ducks. We have much more demand for our eggs than we can fulfill right now. We get about a dozen & a half per day. If you are planning on selling eggs, one of the things my customers love is getting multi colored eggs (blue, white, light brown, dark brown), especially those who have kids. We also have a greenhouse & sell veggie plants in the spring and fresh veggies & berries throughout the summer. I'd plan the size of your coop based on the number of eggs you'd like to get per day, and size your coop accordingly.