The biggest piece of advice I have is that you absolutely 100% NEED an aviary. They are large birds, and unlike parrots who like to climb when moving from place to place, pigeons like and need to fly. There are some great sites on converting large closets into aviaries if you're just keeping a couple - complicated, but you could enjoy the birds inside. If you'd like, I could post links.
One option if you won't have the space for an aviary is to get something related, but not as big as a pigeon. Diamond Doves are small doves that can be kept in very large cages indoors (though even then you should hand tame them so you can let them out for more exersize). They're a lovely color, very quiet with nice vocalizations, and don't generate the mess of pigeons.
Do you want the birds more for companionship, or just to observe and listen to? If it is for companionship, you might want to hand-rear; they're placid animals, but a bit flighty, and they aren't too inclined to bond to humans unless you handle them extensively from a young age. And, you would want more like a few than a flock if they're going to be real pet-pets.
