How does a Kid Earn Money?

Kids have been asking this question since the beginning of time. How does a Kid Earn Money? I remember reading about the toothpaste millionaire when I was a kid and being fascinated by how he sold toothpaste and made millions. This of course was a fictional based book for kids. But I read on line not too long ago about a teenager, fifteen years old, that used a web site she created to make millions before she even graduated high school. The traffic to her site alone made her tons of money through affiliate partner advertisements. It is simply mind boggling.