My sister is currently 13 years old. She lives with my mom and her boyfriend. My mom has moved over 20 times within the past year between her husband and her boyfriend, she is very unstable. She is currently on unemployment and food stamps. My sister has moved middle schools 9 times over the past year, and currently has a 0.8gpa. My mothers husband doesn't work, nor is he getting any assisted benefits. Her husband has 2 police reports filed on him and a DUI from 2 years ago. My mother has 3 police reports filed on her. I'm currently 17 but I will be 18 in July. If I get a job and apartment, I shouldn't have a problem getting custody of her after I turn 18 correct?

It won't be that easy. Especially if mom fights it. As soon as you get settled, you should talk to children's services and let them know that you want to foster your sister with the goal of getting custody.

The largest problem your going to have is a proven track record. So far there is none. So it may take a year to get it done so there is evidence of consistancy.