Here's my tip with Cornish Rocks--they're gross. They don't act like other chickens. They will lie in the food dish and eat instead of running around catching bugs. They can also eat themselves to death, so instead of free-choice feed, many people give them 12 hours of feed/12 hours of no feed. They will grow so fast that they will have bald patches where they get so big they outgrow their feather production. They have the world's stinkiest poo, and LOTS of it.
That being said, they are delicious and they are worth the work, in my opinion.
If they were layers, you'd need at least four square feet of coop space per bird.You'd also need 10 square feet per bird in a run. Since your chicks are meaties, the recommendation changes to two square feet per bird in the coop up to eight weeks. If you keep them any longer, they'll need more room. Space is important for all birds, but with meaties, they will not put on weight well if they're overcrowded and you'll have skinny, stringy chickens for your efforts.
My biggest recommendation to you is to visit the meat bird experts in the Meat Birds, Etc. forum. Those people are awesome!
