Many graduate students, especially after their first year, become teaching or research assistants. Both arrangements allow students to earn money while gaining experience in their field. Some universities even reduce tuition for students working as assistants. In some programs, assistantships are awarded to every graduate student. In others, they are awarded competitively, based on academic performance.
Most schools offer loans under federal and sometimes, state programs.
Many other kinds of loans are available, often under different interest and repayment terms. Research them carefully.