The tuition and fees tends to be higher for graduate programs than for undergraduate programs, and typically the tuition for an in-state public institution is lower than that of a private or out-of-state public institution. Programs that focus on research may have institutional funding associated with on-campus employment, such as teaching assistants, research assistants, and graduate assistants. In addition to direct income to you, they may also cover some or all of your tuition and fees. There may also be fellowships and scholarships offered by the department, university, or from external sources like the National Science Foundation.
Some programs offer limited or no financial support, which may mean that you will need to take out loans. Remember that while undergraduate loans may be subsidized, loans to pay for graduate education are unsubsidized so interest begins accruing immediately.
Regardless of if you know if you will obtain funding, it is a good idea to complete the FAFSA to ensure that you receive the aid you are eligible for.