Now that I am 50, I have a little hindsight. I wish that I had gone to college and became an art teacher. Then I could be doing SOMETHING about art all day, and anything that had to do with studying art would also be furthering my career. Plus, I would have all those teacher benefits: sick pay, vacation time, retirement, etc. I am self employed and have none of that. The day I quit working will be the day the money stops coming in, and it is scary.
Anyway, if I were a teacher, I guess I would be teaching jr. high or high school. I remember my jr. high art teacher. She would set up a project (still life or something like that), turn on the radio softly, and everyone would draw. She would sit in the back at her desk and work on her own art. The students would all relax and chat. Even the bad kids enjoyed it, so she did not have any discipline problems. I remember the kids would talk about all the naughty things they did over the weekend. The goody-two-shoes like me would listen. The teacher never commented on the shenanigans she heard.
Anyway, with money coming in, retirement taken care of, students under control, and still being in an artistic environment all day, I could paint when I got home at night, and work on selling in galleries.
Larry Seilior is an art teacher, and he takes his students on plein air excursions.
My daughter is artistic, and this is what I BEG her to do, but she thinks I am trying to live my life through her. So she wants to do "something else".
The reason I choose this as opposed to commercial art, is that, in an office, you never have a stable job, and you only have benefits as long as you work there. Teachers tend to stay teachers forever.
Now some comments about your other choices:
Art fairs are a LOT of work: packing and unpacking and schlepping every weekend. You never get time off the same time as everyone else. You will not have time for your spouse and children if you insist on making your living this way.
Licensing is a good idea. Kinkade does that. But many people here on WC talk about people stealing their images anyway. Plus, if your niche is successful, there will be copycats. Lots of people besides Kinkade paint cutsy cottages. I am not saying it's a TOTALLY bad idea, but it's hard to make your sole living that way. Plus, how are you going to pay the bills until you get THAT good? That's like saying, "I want to be a hit songwriter". It takes a long time to get to the top.
Commercial artist: Norman Rockwell did it. I just don't prefer it because of the office environment. I have been in lots of offices, and they can be quite back-stabbing. I don't think it's a bad idea though. If I KNEW I would be successful at it, that would be great. Bill Wray is a professional illustrator, at least that is what I gather from his website. And he sells in galleries too.
Making a living at galleries. That would be cool: just paint all day, hang them in the galleries, and watch the money roll in. I would like that best of all. But people are just not buying right now. Galleries are struggling. I just signed up with a local artist, and her work is stunning, which is why I chose her. But she supplements by teaching on the side. Another gallery artist I know supplements by owning her own gallery, selling frames, and teaching oil painting in the back of the shop. Her work is very good. People are just not flocking to their local galleries like they are flocking to their local electronic store. I am 50, and I have to be realistic.
Wow, to be known for my original work and be able to work anywhere in the world. That would be wonderful. I guess that would be my ultimate dream. But how many people can be superstars? I need to think about the practicality of the whole thing. Larry Seilor said it took him 17 years before he was good enough that he could quit his teaching job. I need to pay the bills and raise kids in the meantime.
Good luck with whatever you do!
(Currently, my BIG dream is to paint as well as my teacher, and get in a gallery. Oh yes, and get blue ribbons in the county fair this year.)