It isn’t unusual for a family to come up a little short at the end of the month. How a family handles that situation may matter more than you think. If your family comes up short by $100 every month and borrows that money on a credit card with 12% interest, the deficit in the second month will have grown to $101. The next month, the shortfall will have grown to a bit more than $102. Within a year, the shortfall will be $113. After two year years, $127 and after three years, $143. You’ll also have a new debt totaling $4,308 at the end of 36 months.