I'm super good at shell scripting. I didn't realize I could monetize this.

How do you find "side quest style work" and what does that even mean?

How do you know what problems these corporations have that you can fix? Or how do these corporations find out that they have a problem, and that you are the guy who can solve it?

This is business model of closed marketplace.

Closed mean, client need something fast, but for him accessible only employers.

For example, my friend, have lot of side requests, working as engineer in isp with few thousands clients.

Clients just say him, they want to pay for example to install them wifi at cafe (for which they already bought internet from isp).

Short answer, find something to automate and get permission to work on it. Even better if you are already a consultant at the company. Typically at a large project where there are gaps and developers are miles away. Will the client pay for your time, while you work out the code to get the functionality you want to run? The answer has 100% been yes, they WANT code and business logic implemented.

Good thing, if you like to work in such corporations. This scheme is not working well if you are just have friends there.