[One problem with urban chicken yards is chicken sh*t - it smells! Draws flies, too.]
I’m no farmer, so the question is how many could you keep without them being a pest?
We had probably 6 hens and a rooster growing up... plus a brood of chicks every now and then. When my parents retired out of town they had 2 coops each with 8 hens and a rooster.
Unless you were in the pen...in the henhouse... the smell wasn’t bad.