Bad stuff happens to good people all the time. A recent study found that people who have just $250-749 put aside for a small emergency are able to keep themselves afloat, avoiding overdraft fees, missed utility payments, and eviction.
Do you have a savings account? Start one! $500 is a great amount of money to put aside for a mini-emergency. $500 will cover most (if not all) of a surprise car repair, a huge utility bill, or an unexpected decrease in shifts at work.
Open a no-fee savings account that makes your money accessible to you when you need it -- but not too accessible, you know? The point of this money is to bail you out of a small emergency and give you some breathing room, not to help you take advantage of a killer sale.