Sam had proposed to young Lisa and was being interviewed by his prospective father-in-law.
“Do you think you are earning enough to support a family?” the older man asked the suitor.
“Yes, sir, “replied Sam, “I am. “
“Well, “said Lisa’s father, “think carefully now. There are six of us. “
This joke is included in the Black Book of Jokes. You can order it from here.