more student loan/cost of living loan questions

Hello Everyone, I posted something similar about a month ago, thanks for the replies..but I need more guidance.
I will be starting an acce. BSN at Cal State Long Beach the end of August. As a result, I will need to quit my brand new full time job. I am very excited about school and realizing my dream of being a nurse. HOWEVER - I am pretty freaked out about quitting when I don't know how I am going to get money - and fast.
I will get some federal loans, that will help with tuition.
I am mostly worried about paying my bills. I have looked at some private loans through various banks..but can't seem to figure out what is best. Questions for those of you with loans...
1. How did you know how much to take out (to live off, not tuition) I have done my bills for each month, but do I builid in more money than that to take out for emergencies, etc??
And advice on this would be appreciated. I have student loans from my first degree, but my parents handled all that and I just had gov't loans, not private ones.
Thanks so much!
Jen