A son asks his father what is the meaning of “in practice” and “in theory”

“Il show you son. Call your sister.” Says the father”Daughter would you sleep with a man for a million dollars?” Asks the father”Yes of course, that is a once in a life time opportunity!” Answers the daughter”Okay son now call your grandmother” Says the father”Grandma would you sleep with a man for a million dollars?” Asks the father”Yes I would! I would do it for you so the family can thrive financially!” Answers the grandmother”Okay son now call your mother” Says the father”Wife, would you sleep with a man for a million dollars?” Asks the father”Yes! We could buy a bigger house and have loads of vacations!” Answers the motherThe father looks at his son and responds “See son, in theory, we are millionaires but in practice 3 whores live in our house!”