I started Hacker Newsletter [1] almost 14 years ago and sent out the 647th issue today [2] to 58k folks. It took over a year to break 1k subscribers and a few more years to get to that type of revenue. I could do a lot more with it and plan to one day, but really only focus on it a couple hours each week when I build the issue and talk to sponsors.

1: https://hackernewsletter.com 2: https://mailchi.mp/hackernewsletter/647