This couple has been disagreeing over how to spend their fun money . One of the best parts of adult life is having fun money left over at the end of the month to spend however you wish. After you've paid off the rent or mortgage, car payment, and bought all your groceries, having an extra 30 bucks to use on something special feels like the perfect treat. Some of us buy new shoes or clothes, while others head to the movies or plan out a weekend trip. Others love to upgrade to the newest technolo…