After your tank is cycled, and you have the fish you want in the tank, what do you do with the starter fish? Id feel bad just flushing them or something. Is it ok to keep them in the tank?
It is ok to keep him in the tank. You should never flush a living fish. If you don't want him, you can try to sell the fish back to the fish store you bought him from.
Most LFS will take the fish off of your hands. But they probably won't pay you for them. I just had to donate two of my fish to the LFS because of harassment issues (they were harassing other fish).
I would just keep the starter fish; if they survived the cycle, they'll probably survive any mistakes you make in the long run as well.