Well, if you want to keep him, as long as you don't mind him crapping everywhere, just let him roam the house and backyard freely.. This is the best way to keep a bird. But it still would be good to have an avery (not a cage) for him for the night etc...
And if he grows up, and flies away one day, don't be sad, cos you know you SAVED TEH BIRDIE!!! YAY!!
We had a Magpie once (Kinda like a crow, but has white patches, and instead of crowing, it warbles, and sounds WAY COOL) and we did exactly that.. we brought him up, and when he was an adult, he flew away. And a year or so later, he came back, with a family, and his little tribe kinda lived in our front garden. But there was another tribe of birds nearby, and they always had wars.. it was cool to watch... KEKEKEKEK!!!! ^_^;