I'm sure others will chime in, but you might want to try searching side hustle or hustle. I think they might pull up some relevant threads.
I've earned a bit doing surveys on MTurk, mystery shopping, and other random gigs that come up. I think there's some potential in buying and reselling on Amazon (others on here do this and seem to turn a good profit).
However, I think the more important question is how are you going to raise your normal income. If the commission thing isn't working, maybe it's time to consider a change in your primary employment.