He looks like a boy. Hens over 6 months can have that recessive single comb so large, but at just 15 weeks, plus you saying it came in early, it's a boy. If you said that that comb just came in the last week, it might be a sliver of an early maturing hen, but otherwise, it is a rooster. If you look into the roots of his saddle area and on the neck, I bet you'll find glossy feathesrs coming out of the pin feathers. He has a light complexion, so that comb is pretty red and will likly only get redder. Listen for crows. But even if you are limited 3, do chicken math. Banties are 2 for 1, so you can have 6. Plus, as long as roosters don't crow, you can hide them in the garage. LOL