You will need enough disposable income to pay those creditors that are required to be paid. The rules that govern what creditors have to be paid and how much are in the Bankruptcy Code. It depends on both the nature of the creditor and the debt. For example, if you owe $60,000 in child support arrears, you will need at least $1,000 in disposable income to pay off the child support over 5 years. A qualified bankrutpcy lawyer will help guide you through these rules to help you determine more precisely how much you need.