Well, if you did a little bit of research, you would find this question on here a LOT. There are a lot of people aspiring to be YA authors, including me.
I suggest majoring in Creative Writing, maybe even getting a masters as well. Just taking classes will help, but not as much.
Also, complete...
Find an agent first. Talk with them. Make sure you speak with more than one agent, also. You're going to get different offers and some are going to be better than others. Besides, you've got to find the one YOU want to work with. Worry about that before worrying about pay.