Key Values (https://www.keyvalues.com) is a one-woman show (oh hi!). I started Key Values as a side project two years ago, but it quickly turned into my full-time passion and business. I'm doing ~$30k/month and it's almost all profit since I don't have an office or any employees. I recently talked to Courtland of Indie Hackers (already mentioned in the comments) about how I got here: https://www.indiehackers.com/podcast/086-lynne-tye-of-key-va...

I would never have started Key Values w/o Indie Hackers, so I highly recommend you spend some time there. It's a bottomless treasure chest of inspiration.