There are many threads on this topic. Basically, if you school counts your stipend against your cost of education (i.e. as a scholarship), it reduces your FAFSA eligibility by that much, thus you wouldn't be able to borrow very much or nothing at all. If your university counts your pay as payroll and does not subtract it from your COE, you are eligible to borrow up to that much. For me, I can borrow ~$20,000 a year in FAFSA on top of my stipend.
In other words, ask your financial aid department.
-G