When you are a public employee, there are certain union/collective bargaining requirements that may restrict your second employment or the city or specific public entity may prohibit outside employment that is a) a conflict of interest with your current employment or b) discredits the position which you hold publicly.  So if you are a firefighter, and say you work as a pyrotechnics person, there may be issues with that.  If you are a public employee working in financing for example (say an auditor) and you wind up being hired as an auditor for a company regulated by your public agency, it would be a conflict and may discredit you as a public employee.  Statutory schemes can not only prohibit this for public employees but corporations can also require their employees to sign non-compete agreements.  It seems in your case it may be a case by case basis.  You need to figure out if your outside position would run afoul of these issues and bring it up to personnel to see if you can hold that position.  If you can, great! If you cannot, you need to decide which position is right for you to provide for your family.