A little boy comes home from school one day with a troubled look in his eyes. His father asks him what the problem is and the little boy explains to him that he has a homework project that he doesn't know how to do. The father asks what the project is. The little boy explains to the father that he is supposed to report to the class tomorrow morning the difference between theory and reality.
The father thinks about it for a little while and says, "Here's what you do: go upstairs and ask your mother and your sister if they would have sex with a strange man for one million dollars and see what they say".
The little boy does exactly what his father instructs him to do and returns five minutes later with the answer. "What did they say?" asked the father. "They both said, 'YES'", the little boy reports.
The father nods his head and says, "Okay, son, here's the difference: In THEORY, we are millionaires whereas In REALITY, we're living with a couple of whores".