What sideline can white-collar workers do?

This is the same as knowing knowledge. If you have outstanding skills, you can use them to make money.

But if your skills are what most people want to learn, such as teacher Lulu is a water conservancy project, CAD is slippery, but useless. Not many people need you to draw for him.

Therefore, the more your skills are needed by everyone, the more you can realize them. Think about how many people need your skills.