I dont think OP ever said it would only be one chicken, he said "let my chickens roam freely on the balcony"....I dont think he is even here anymore lol
I'd like to be a fly on the wall when the neighbors below OP are having a fancy dinner party on their balcony and wood chips and chicken poo plop in their wine glass from foraging......or better yet on their heads....lol
I have to wonder if the OP isn't setting back laughing at what a ruckus they have caused or if they were actually serious? But in all seriousness, I strongly advise against this, and like others, I am sure it wouldnt be allowed by the landlord anyway.
What kind of life would it be for the chickens to be enclosed in a balcony all their life, without any ground or grass to ever forage in? Will they have cover? I can see other birds swooping by for free breakfast, and then you have a mess on your hands. They will still need a coop to roost and...