From the Making Of issue to the series The Private Eye, written by Brian K. Vaughan, illustrated by Marcos Martin, and colored by Muntsa Vicente. The issue details via email the process leading to the comic's creation, and in one of the first emails Vaughan asks Martin a question.
"Brian K. Vaughan: 1) Seriously, how long are you okay with not getting paid?"
That question is one of the most important and best kept secrets in the world of comics, and it's also one of the most misunderstood. I absolutely agree that artists (of every kind) need paid, that people who do hard work should be paid for the work, and finding paid work is one way to find more paid work, not to mention pay bills or get fun stuff like books and coffee. Sometimes in order to get paid work there has to be something created for free. It's an unpopular opinion, I know.
The BKV/Martin example also isn't the best because Brian K. Vaughan is one of the most successful comics writers currently working, most likely to ever work in comics. Marcos Martin is not hurting for work either. They have paid work, they have the freedom to do experiments like release an independent digital comic for the price of Oh-Geez-Whatever-You-Feel-Like dollars, so doing some free work isn't going to mean they go without a meal.
I've noticed a trend online where current comics professionals tell the hopefuls that they should never do work for free. I'm not even saying their message is wrong, just that it's slightly unrealistic, and pretty limiting. It also scares me that there could be a creator who thinks writing, drawing, inking, or creating in any way without getting paid is a waste of their time. That has never been my experience.
I think the message for burgeoning comics professionals, in whatever specific role being chosen, is Choose carefully which projects you'll do for free. Maybe the project is something you do alone, maybe it's a collaboration with likeminded creators. But for comics to be noticed (for any works of art to be noticed) they have to exist.