Top of the list for a stipend -- how likely is it?

[kimedieval]

Was accepted to my dream program, yeehaw. 

I was put at the top of the list for a stipend, so if someone declines the offer, I get the TA-ship or grader position. How likely is it that this happens? I ask because I also got a job offer for a job I could technically do during my PhD for living expenses (no tuition expenses). I don't want to accept it until I know that I can do it for sure