As someone who is making a career in webcomics here's what I think will make money: Rare and Valuable content.
By rare I mean creating stories that no one else is making or at least not in that particular way. It requires study and mastery of not only story craft but of art and the methods of visual storytelling.
Valuable means it's something that brings entertainment to the reader in our case. It means creating something people will buy. This also requires research and a lot of self-awareness. Because it has to be valuable to you too. Trust me when I say making something you don't care about just to earn money is NOT worth it. The content you create must bring some kind of value to you and the reader. Remember that you are your first reader, your first fan. See what others love and are buying, then see if that's something you love too. If it is then you know where to focus your efforts.
Making money in the arts for a lifetime means constantly sharpening your skills. There is a million and one ways to SELL what you make or the service you provide (commissions) BUT, you need to offer something rare and valuable to the end consumer.
I firmly believe you can make a living out of anything if you work smart and hard. That means researching the hell out of your field on what others are doing and what skills they have that make them successful cause that means You need those skills or something similar.
Also consider what you mean by living. Is it modest living in a comfortable apartment or the very wealthy and lavish life? Cause let me tell you that anything that pays a lot of money consistantly requires an effort on your part that is of equivalent consistancy and expertise.