I run one, a minimalist personal finance app. It's about 11 years old at this point. I built it up as my full-time gig and ran it initially for about six years

I run one, a minimalist personal finance app. It's about 11 years old at this point. I built it up as my full-time gig and ran it initially for about six years. At that point: A) I had hired someone part-time to do customer support; B) the feature set was stable enough that it didn't need constant attention; C) I was missing working with people. So I moved out to SF and started working with a startup as an engineer. Enjoyed that for two years, then moved on to another startup where I was for three years (first as an engineer, then had a chance to move into management [which I also enjoyed, but where I missed making things]). This past October I left that startup to go back to working on my own thing. Revenue coming in to the app dropped significantly while I was doing other things, but since coming back to it I've rebuilt it (well … 90% of it) and am soon going to be shifting focus to improving business operations (in addition to building out some new features). My hope is that within a year or so it'll be back up to its earlier customer levels, but I haven't spent a lot of time forecasting that, and growth could be slow. It'll be a while before it'll support us living in SF, but that's somewhere on the horizon. What worked for me might not work for you (it was a long time ago!), but in case it's helpful, I built a very basic MVP (literally a spreadsheet) to scratch my own itch and then shared it, for free, online. (At the time I wasn't thinking of it as a business, just as a way to help people.) It got a good amount of traction. I was able to build on the attention the free version got (and the feedback people shared) and to develop a web-based, subscription-based version that required less work and gave more value to customers than the free version. I haven't ever taken funding, and am so, so glad I haven't.