I can actually question that statement based on a personal experience.
Here`s the story if you are curious:
So, one day, in college i saw a poster about a site where you can design t-shirts and sell them online, so after figuring out how the site work, i made a design and did the digital illustration on the university`s computer. The site gives you a commision for every sale a shirt with your design is made, the costs were handled by the company. Some days after my first design got approved, i started receiving some commisions.
So, i was able to make some cash without any aditional cost, just by noticing the oportunities and using the tools that were available. Is not like i became rich, but it paid my Hearthstone addiction when i played