The cost of attendance (also referred to as the student budget) includes allowances for room and board and books and supplies. When the financial aid (including loans) exceeds the school charges the college will let the student withdraw the credit balance to pay for these expenses.
Be sure to borrow federal first. Federal loans are less expensive, more available and have better repayment terms than private student loans. The Stafford loan (a student loan) does not depend on credit history. The Parent PLUS loan does depend on credit history, but it does not look at credit scores. Instead, PLUS loan eligibility depends on the absence of an "adverse credit history" (e.g., default, foreclosure, repossession, tax lien, wage garnishment or certain other derogatory events in the last five years, or being 90 or more days late on any debt, except for mortgage or medical debt which has a 180 day threshold). Congress recently increased the annual and aggregate limits on the unsubsidized Stafford loan. The PLUS loan can be used to borrow up to the full cost of attendance (minus any other aid received).
The unsubsidized Stafford loan and the PLUS loan are available without regard to financial need. You do not need to be poor to borrow from these loan programs.