I have made a total of $100 CAD over the course of... 5 months by selling a $10 plastic tool for strollers on Facebook marketplace. These were printed at my local library before I ever owned my own printer.
Now that I do own my own printer, I've just been enjoying printing very long prints that I couldn't at the library.
All that said, there are niche markets where you can fill a need and you can earn some slush fund money without taking on much stress.