It will vary from school to school, not person to person.
Each schools' fin. aid. office makes a determination on a monthly cost of living for a "typical" student in their school. They then multiply it by the # of months the program runs each year (most schools run 9 to 11 months per year). They do not take into account your income or family status, it's the same number for everyone.
When I was gathering Fin Aid info on various schools last year the annual number seemed to fall between $15k and $19K. Each school can tell you what their number is for this year. Divide that by 12 months and you have your monthly number. You can borrow this school-determined amount, in addition to your tutition books and fees.
There's lots of other threads on financial aid that can answer questions you may have.