I started a self-funded SaaS business fairly late (in my 40s). I was tired of being dependent on others, especially as others mostly failed me in the past. I wanted to be independent: no investors, no bosses, no employees. Just me.
It took five years of slow growth to get to a stage where I didn't have to worry about revenue.
Do I regret it? Hell no! It's the best decision I've ever taken in my life.
I am now very happy with where I am: I have a business that depends on very few external factors and runs well. I don't have to worry about investors doing crazy investory things. I don't have to worry about employees pulling crazy employee stunts (believe me, I've seen a good number of those in the past, and the entitlement of many employees is absolutely crazy). I don't have to worry about user numbers, only about paid subscribers and maintaining slow revenue growth. Nobody pushes me for crazy growth.
Most importantly, the business model is simple: my customers pay me because my software improves their workflows. That's it. There is no "monetization", no shove-it-down-your-throat marketing, no tracking, none of that unpleasantness that seems to be dominating today's world. If they like the software, they pay a subscription fee, if they don't, well, they don't, and I have a problem. But so far it seems they do :-)
The only thing I had to carefully manage was my engagement: it's easy to get pulled in and work crazy hours, because in a single-person business there is always much more to do than you can possibly ever do. You have to become good at prioritizing, which means identifying the single (ONE!) most important thing at this moment and focusing on that. But you also have to accept that most things will not get done and be OK with it. That was hard for me, but I learned, and I keep sane hours and a good work-life balance.
I'm posting this just to provide a counterpoint to many negative comments.
PS: if I were to provide one bit of advice to aspiring entrepreneurs, it would be: look for a business that delivers high value to customers with money. So don't start a B2C business that does something easily replicable with a low value. B2B is where it's at.