I've started growing breast tissue already. There isn't much to it; it doesn't look like breasts, it just looks like I have slightly bigger pecs, as if I'd been doing pushups for the past three weeks. But they're soft, and sensitive - when I press the area with my finger, they feel sore.
At this point, my cup size is null; if I was caught topless, no one would even know I had breast tissue unless they felt me up.