Yes. You have to learn a skill with demand that cannot be met. That is the easiest way to get side work.

Learn Salesforce development. I've accepted a new contract role that is full time hours and my older employer straight up told me, "We cannot match your new hourly rate, but here is still a raise. Feel free to work on things for us whenever you want, whenever you have time, remotely."

I'm nothing special, an average developer. But businesses cannot find enough Salesforce developers, so some take what they can get, even if it's part-time.