I believe that a teenager can start making his first money at any age. In order to make money there are many jobs. For example, you can walk with other people's dogs, help younger classes with homework for a small fee, post flyers and ads, work as a courier. Work can negatively affect the study only when it takes the teenager all the free time. It is quite possible to do some work and earn some money, because at the moment younger and more active children and teenagers are employed.