Wow.... people are so dam judgemental. Two yellows in a 75g is a bit excessive and will most likely result in fighting. Breeding clowns can take an extremly long time if it ever happens (I have had the same pair for a year, they dont go in nems and dont breed).
I am a strong believer that their are more than one type of E. quad, this is shown by the fact that some of my E. quads get along and dont stress eachother out, even different colors, and some of my E. quads have to be moved to another tank because they cause chemical warfare with eachother. The ones that split often usually dont grow much larger than a softball. I feed all my nems every other day to every day (mysis/my own seafood mix). They get fed with the rest of the tank and do very well. With that said they dont get fed a lot, the equivalent of a few mysis every day or two.
You can cause them to split just by keeping them happy and feeding, or by stressing them out, or by cutting them in half. BTA's are known for their ability to heal them selfs, and if you do cut yours their is a good chance with proper care both halfs will survive. Do not cut them If you do not understand the process or the care requirements, they will take a 1-3 months to really heal, expect that as a turn around before you could sell one.
Do not count on getting $100 dollars for any of your RBTA's on your local forums, its possible but unlikely. Expect to get more like 50-75$ for good looking ones.
To the guy who thinks mowing a lawn once a month gets you more money than a salt tank... pssh, seriously you know better. I have a large tank, its not cheap to keep it and I am not trying to make any money off of it, but that does not stop me from making $50 dollars everytime someone comes over and wants a few frags (I sell stuff cheap). The cost of keeping a reef tank can be almost completly offset by selling quality frags from the tank.
I do however agree with most of the people here, you should just let the nem split naturally, when it does sell the split if you want, or more intellegently, wait until they both split again and you have 4 to start selling them.
Just my .02