How can i get my sag card while im still young?

i have been working with the non union for a while, and want to try and work with the union in order to boost my acting career. it's been my dream to become an actress since i was little, and i've been getting professional training since the 5th grade. i'm signed with 2 agencies but am currently working with the non union and they hardly send auditions, they only come from time to time. right now im 15, and it was my new years resolution to try to get it before i turn 16. i think im ready for it too because my parents have done a lot for me to reach my dream and i think i've had a lot of training too. i live in maryland and it's just really hard to get roles as extras in major movies, and i know i need 3 sag vouchers in order to be sag eligible. i also thought about joining the aftra in dc but it just costs a lot of money and i feel bad that my parents have been spending a lot on me so far. any suggestions or tips?