John Jonas on managing workers with multiple jobs: ask them directly why they need the extra income, understand their financial situation, and use incentives to help them stay. Multiple jobs work short-term but burn people out fast.
Chapters
So for me, I've always been able to work it out with them. I've always been able to keep them working for me. Sometimes their other job fizzles. Sometimes I've been able to incentivize them to work just for me. Sometimes they maintain both jobs and keep their productivity up, although this usually doesn't last super long because it's really hard to work a lot of hours and maintain productivity in bulk. But in all of this, to me, asking the question is the key. Ask do you have another job? Ask why they have another job. Ask about the financial situation. They may not want to tell you, but they they're likely to tell you. And realistically, you have ability to improve their financial situation or to improve their life situation. There's all kinds of good that comes from asking questions in this situation. See if you can improve your worker's life, thus improving your business.