People in a job, what would interest you to pick up paid p/t work?
If you're full-time employed in a job, what would prompt/compel/interest you to pick up a few hours a week of paid work with another company? Eg say you're a devops engineer and a startup needed 10h/week of help in something you can do well.
Interesting project? $$s? Would it have to find you? Seeing what's out there for your next job? Would you try to look for it?
I'm not quite who you are asking about, but I'm a programmer who already does part-time work (only). I think the only issue about it, is that it is difficult to find clients (fortunately once I find them, I tend to keep them). Most people who need a developer, are not accustomed to the idea of having one support them in some way part-time. In some cases I've gotten a client who was looking for a full-time dev, and eventually gave up and agreed to hire me part-time out of desperation. But most potential employers are not familiar with the idea of hiring a dev part-time, and because it strikes them as weird, they shy away from it.
I'd do it to make connections, but I would need to make some small amount of money. For 10hrs/wk I'd expect $1k/wk if it is something I specialize in.