If you're already a software engineer earning a normal salary in the US (several assumptions there), it's really hard to find side hustles that pay at or above the hourly wage that your employer has already committed to. I personally think that it's a good idea to focus on building a small lifestyle software business over the course of several years. I wrote a long series of blog posts about this over here: https://overthinkingmoney.com/2023/05/02/start-a-business-no...

My first company (Skritter.com) fits this mold. It's been growing slowly, but steadily for more than 15 years now. In the first couple of years we were able to generate low five-figures per month, now it's substantially higher.

There are other ways to earn cash outside of tech, but most of the common suggestions (drop shipping, affiliate marketing, laundromats, etc) are mostly terrible if you really do the analysis.

For better or worse, low risk generally means low upside!