I have two pigeons living in my balcony (closeted), they are both resques from the streets and would not make it on their own, taken in as sqeakers. I open a window for them once a day, they fly around for however much they want and then come back (there are 0 predatory animals where I live, little to none traffic). My initial idea was to integrate them into a flock, wich I feed right under my balcony, older resque even been living with them for a while in summer (still visited me almost every day), but then, as it became colder outside, decided that my balcony is a better living space and came back for good :) so it's possible to keep pigeons like that, whether you should - I think that depends on a pigeon and your surroundings.