I've hired a bunch of people through fiverr to do small gigs for my writing (eg copyedit, add a few jokes, do illustrations). One "dumb" way to make a bit of extra cash for programmers could be to take on gigs like that. Depending on your skills, there are plenty of web design/automation gigs that you could offer there. This doesn't need you doing time-consuming marketing or sales, or chasing consulting clients. It also doesn't require you to come up with a SaaS product. On the other hand, the gig market tends to be a race to the bottom in terms of prices, so the income won't be that amazing, but then again you asked about dumb income ideas.

a slightly less dumb idea is to write a book. it's more upfront/unpaid work than when doing gigs, and more risk because it's up to you to create a good story, but significantly less risk than building a SaaS system. I've self-published five books so far, and books have three benefits over the gig economy idea:

1) you get to learn a ton of new stuff while researching for the book. writing a book is effectively forcing yourself to learn

2) even if books do moderately well, when you self-publish you retain most of the profit. my passive income from previously published books is roughly 3-4K USD per month now

3) books have an extra effect that they tend to bring name recognition and incoming work for consulting, and that can last a few years even if you don't plan to freelance and work as a consultant at the moment.