Humorous story of potential and reality

A childrens comes home from school with a writing assignment. They asks there father for help. "Dad, can you tell me the difference between potential and reality. " His father looks up, considerately, and then says, "Let's make an expression out of this. Go ask your mother if she would sleep with Rob Smith for a million rands. Then go ask your sister if she would sleep with Steve Gusy for a million rands. Then come back and tell me what you've acknowledge."
The children are confused, but they decide to see if he can figure out what his father means. Then they goes to his sister’s room and asks her, "Sis, if someone gave you a million rands, would you sleep with Steve Gusy? His sister looks up and says, "Absolutely!” The children go back to his father and say, "Dad, I think I've figured it out. Potentially, we are sitting on two million bucks, but in reality, we're living with a couple of Prostitution.”