Let's say money as a proxy for "being non-trivial" or worth enough for someone to pay for. I don't know how else this can be signalled.

"Side" in the sense that my main income coming from somewhere else, aka my "normal" job

I interpreted it as "enough to live a comfortable life".

Money is part of how you get there, but it is not a goal in itself. Many start businesses where money is the main goal, and where the amount that you are satisfied with inevitably shifts once you get richer