What age should i join as for CMT?

Hi I was wondering what age would be right for joining as a CMT. I know on the website they say 16+ but I was wondering if it would be okay to get a separate degree first and join at 21 instead so I have something to back on if anything happens or I dont enjoy the role.

Would there be other people there my age or would everyone be 16? And is doing a different degree first stupid if I could get a paramedics degree in the army anyway?