I live in a non-HOA community, thank the Good Lord, and have no ristrictions from my city. I intentionally got two cockerels, a Black Copper Marans at two days old and a new Hampshire at a month old. Both were raised by older hens, so are very respectful and wonderful. My baby has been around all of our chickens and turkeys since she was about six months old and we've only had one problem. At about a year old, she was feeding them grapes and one of the cockerels got her finger trying to get the grape. Otherwise, we have had absolutely no signs of aggression.
I wanted each rooster for breeding, primarily, but the other reasons mentioned also played heavily in to it. Protection, flock harmony, and beauty. My flock is significantly calmer and I haven't seen or heard of any predators in my yard. I have 11 hens and 3 cockerels, plus three more babies about two months old.
I have put chicks out with the flock as early as a week old without problems. As long as the temperatures are ok, I will put them out almost as soon as getting them. My flock is constantly adding or subtracting members, so maybe that plays heavily in to their acceptance.
I don't have any really good pictures of my cockerels, but here are two of my BCM, Ninja. As a chick, he was one really quick, sneaky little guy and would be inside the house before you could blink. I use more of a hands-off approach than many others, so they associate me with food and not handling like the pet owners do. I'm completely ok with this, since it also makes them less likely to be stolen! He was about six months old when these were taken.