Ask HN: Those making $500/month on side projects in 2021 – Show and tell

I love these kind of posts. Here are some interesting ideas for side-gig:

1. Books. There are quite a few books there, books for babies, books about iOS dev etc.
2. Mining Cryptocurrency. This comment got a lot of attention.
3. Apps. Too many but was glad to see Mac apps generating decent income.
4. Music. Decent income from YouTube content ID payments according to this comment.
5. DIY biologist. Seems fun.
6. A lot of SaaS or content sites.
7. Flipping items from thrift stores on eBay.