Yes, you can have negative money. It is called being in debt. People that have negative money have more bills to pay than money in their bank accounts. For example, if you owe $500 to your parents but only $150 in your savings account to pay for it, you are in debt by $350. It is a dangerous thing to be in debt, as who knows how long it will take you to get out of your debts and have more money than bills.
Money Smart Kid