It took my clowns around 2 years to mature and form a breeding pair. They now lay eggs regularly (about..once every 2 weeks or so) but I don't bother removing them. They lay them on a piece of rock right next to the torch coral that they host. I let them go until they hatch, and let other things in the tank eat the larvae I guess. The following morning when they are gone, Mom and Dad are back picking the rock waiting for the next round.
If you are interested in a breeding pair, I would buy the two together, that way they can pair off together (if they will, they don't always pair up). The female will get much larger and agressive while the male stays small and passive. I would not expect breeding to happen in your first year of having the fish, especially if you get them when they are tiny. They need time to mature sexually and form a solid pair. When they do though, you might notice an increase in activity between the two fish. The female will get plumper in the belly. The male will start agressively cleaning a piece of rock or slate that you provide. Then one day there'll be eggs there.
If you get older fish together, it's possible to see breeding in under a year, but I wouldn't count on it.
HTH
