It all boils down to contacts, I found. Knowing people, having others spread the good word about you, and also hanging around with business people whom you might solve a problem for randomly.
I made 600 EUR a few years ago with a 3-line PHP code change and an advice how to asynchronously load JS on a front page of a website. I can’t have spent even 2 hours on the whole thing. Still experience that high every now and then when I remember it. 
