Seven years ago I solo-started an automatic time tracker for programmers called WakaTime [1] and launched here on HN [2]. Partly from listening to developers too much, I waited way too long (almost a year) before adding a paid plan, but now it generates more MRR than an SF developer salary not including stock options. Technically I make more from RSUs and stock from past startups as a regular employee, but if I wasn't lucky with those then it would be my highest income stream.
For anyone thinking it's egregiously difficult to start a solo-project: You're right, but if you stick with it your persistence will pay off. For solo-products, I think grit is the deciding factor between success and failure.
I've used Wakatime now for a few years (I highly recommend it), and have been going through one of the toughest projects of my life in the last 8 months. At one point I reached ~16 hours per day (for only a couple of days).
This kind of output is not sustainable for more than a few days without incurring serious problems from it. I have now gone back down to a more normal 6-9 hours per day.
Not sustainably... I've done that myself: it's hella fun but towards the end of the week the code stopped making sense and had to sleep for a whole day. WakaTime is very accurate so my daily average is only 4 hours of actual typing per day:
There were several stages of MVP. First usable version took a month and half to build and public launch with 2 IDEs supported was 2 and half months after starting to build.
Unfortunately I don't have WakaTime data until after finishing the Vim plugin, but everything after that I can see how long the actual coding took by dogfooding.
1: https://wakatime.com/about
2: https://qqrl.tk/item?id=6046227
For anyone thinking it's egregiously difficult to start a solo-project: You're right, but if you stick with it your persistence will pay off. For solo-products, I think grit is the deciding factor between success and failure.