"Potential & Reality" joke

POTENTIAL VS REALITY
___________
Johnny comes home from school with a writing
assignment to define and subsequently explain the
difference between potential and reality. After
getting nowhere on it for 2 hours, he finally asks his
father for help. "Dad, can you tell me the difference
between potential and reality?" His father looks up,
thoughtfully, and then says, "Go ask your mother if
she would sleep with Robert Redford for a million
dollars. Then go ask your sister, Suzie, if she would
sleep with Brad Pitt for a million dollars. Then come
back and tell me what they said."
The kid is puzzled, but he decides to follow his
father's guidance. He goes downstairs to the kitchen
and asks his mother, "Mom, if Robert Redford gave you
a million dollars to sleep with him would you?" His
mother looks around slyly, and then with a little
smile on her face says, "Yes, I would." Then he goes
back upstairs to his sisters room and asks her, "Sis,
if Brad Pitt gave you a million dollars, to sleep with
him would you?" His sister looks up and says, "Omigod!
Definitely!"
The kid goes back to his room and father and
says, "Dad, they both said' Yes.' " The father sits
back and says "Now son potentially, we are sitting on
two million bucks, but in reality, we are living with
a couple of whores."