It varies. One or two little things might get past. One BIG thing might not. Even a LOT of very small things can do you in. One guy got refused a security clearance in Intelligence School when I went through because he had TOO MANY speeding tickets! He had so many that they declared him “unfit” due to lack of discipline, and too apt to constantly break the rules. That, however, Does make sense.

Go ask your local recruiter, he will tell you.
Also, STAY OUT OF TROUBLE! When your young, you have no idea how many bridges you’ve burned until you get to those bridges.

It can be very difficult, you can be turned down for a secret clearance for traffic tickets, but all is not lost you can go in serve your first term, re-enlist and if you haven’t had any trouble and performed well then maybe you can request the job you want.