Spike's got it right.
Unfortunatly with O's they dont reach reproductive maturity untill 1-1.5 years, mine didn't breed until they were around 8"+ and sexing is essentially isomorphic. Your best bet if your just wanting to get a breeding pair as soon as possibly is to find someone getting rid of a breeding pair. A word of advice on that, if your looking for a "breeding pair" of Oscars, make sure you buy/trade for a "PROVEN" breeding pair where the fry actually hatched. I have seen 2 females act like a breeding pair, one will lay the eggs and you would swear they were 1M/1F and the fry will never hatch. I have seen a few people find this out the hard way. I would not consider them for a beginning breeder, as they can be difficult due to their sexing and the size they have to be before reaching breeding maturity.
If you have the room, I would start off with 6 -10 depending cost, bloodline, and size and go from there. I usually start a 'family' s I call them with about 8 O's in a 125g. Of course you dont need that big of a tank to start, but the wife gets pissed when she has to help me move O's that are 8"+ she always gets soaking wet LOL. I hate changing tanks too, so if i'm lucky enough to get 2 pairs in the group, I just divide the tank with some plastic egg crate and their set.
I hope this helps, goodluck with your O's
L8r
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