Lil Johnny......

Little Johnny asks his father for a $200 bicycle for his birthday.

Johnny's father says, "We have an $80,000 mortgage on the house, and I just got laid off! There won't be a $200 bike this year."

Two days later, Little Johnny walks out of the house with all his belongings in a suitcase. His father asks him why he's leaving.

Johnny says, "Early this morning, I was walking past your room, and I heard you tell Mommy that you were pulling out, and Mommy said that you should wait because she was coming too, and I'll be damned if I'll get stuck with an $80,000 mortgage!"

Little Johnny go's up to his dad and says to him 'Dad, what's the difference between in principle and in fact?'
The dad takes a second to think how best to explain this, and comes up with the follow scheme.
'Johnny why don't you ask both your mom and sister if they would do the neighbour for a million in cash'.

Johnny runs up to his mom and asks her, does the same with the sister and quickly returns to his dad.

'So what did they say Johnny?' says the dad.
'Well, they both said they would sleep with the neighbour for a million in cash' replies Johnny.
The dad frowns.
'There's your answer then Johnny, in principle we are millionaires. But in fact, we got 2 whores in the house.'