You are responsible for repaying the principal balance of your student loans after you have completed your degree or cease to be enrolled at least half-time (less than 6 credits).
Federal Direct Stafford loans allow you a six-month grace period after you cease enrollment or drop below half-time, before you have to begin repayment.
Federal Perkins Loans allow you a nine-month grace period after you cease enrollment or drop below half-time, before you have to begin repayment.
Your lender or loan servicer will notify you when repayment is scheduled to begin. Be sure you keep your lender informed of any change to your mailing and/or email address to ensure you receive correspondence from them.