Well, almost all saltwater fish are hard to breed, even if they do they take a lot of work to rear. You can get clownfish, banggai cardinals, etc. to breed quite readily in some cases, but raising them is another story. They need many types of foods like rotifers, cyclopeeze, etc. and are usually fed 3 times a day. On top of that you need seperate tanks, a lot of equipment, and some experience with saltwater because water parameters need to be close to perfect.
Trust me, you'll read about this and think it's easy, but when it actually comes time to raise babies you find it's one of the hardest things in this hobby that you've come across, take me for example. I just had my seahorse have babies! I was so happy then you know what, I didn't have rotifers, cyclopeeze, copepods, a seperate tank set up, and alll that junk so now I only have 4 left! WEll, actually about 2 from the last time I counted. I had to settle with sticking them in a breeder net and feeding daphnia and starting up a thing of brine shrimp.