Billy and Mary

9 y.o. Billy goes next door, "Mr Jones, Mary and I want to get married."
Mr Jones thinks this is real cute, a pair of 9 y.o. kids wanting to get married so he decides to play along.
"Where would you and Mary live if you got married."
Billy, "We both have our own rooms but Mary's is bigger so we plan to live there."
"What would you do for money?"
Billy, "Well, if we pool our pocket money we should be able to get by."
Mr Jones is tickled pink that the kids have everything worked out so he asks, "What if a little one comes along?"
Billy replies, "We have been lucky so far!"