I've done a few of these for people at home (albeit not quite so complex) and for myself. I built the application/infrastructure monitoring systems where I work as well. As one poster said above, document everything, even the commands. It works, although it is tedious. But there is a certain joy using something you created, even if it is something of a "labor of love" to maintain it.
I want to get out of IT after 20 years, but there is no way I will stop tinkering with OSs, Raspberry Pi IoT devices, SoC, light coding, etc. It's different when it's a hobby than when you're faced with time constraints, budgets, and nagging bosses.
A project I'm about to start at home is taking an existing 1080P dash cam (front and rear) that features great night vision and hack it using a Raspberry Pi that handles motion detection, sends stills, and uploads to the cloud. Sure, I could go buy an extant system that just works, but what's the fun in that? It's like Legos. I could go buy my kid a fully-assembled car or spaceship, but I'd rather him learn how to follow instructions, see cause and effect, and experience the pride of a job well done. YMMV. There is something really uplifting in seeing "complex" technical stuff working that you yourself built. It doesn't even have to be as good as existing tech.
It's probably a function of to whom a one man band can effectively market. Consumers don't buy SaaS and a single person couldn't afford a consumer level brand ad campaign anyway. Big companies mean big company sales cycles and demands - procurement departments, compliance etc. Other SaaS companies are easier to find in places like HN, and they're maybe more predisposed towards buying from lone hackers like this one.
