Using the 4% rule this money could earn $68 per year for life. If I did it for one year straight, I could potentially see a permanent income of $816 every year for life. Just from this one side hustle.

But yeah better, enjoyment of the side hustle is important. So you need to factor that in. Not much happiness to do a job all day, then hustle on something you dislike afterwards. What I am saying is that money is not the only consideration.