Financial support is part of your formal offer of admission. Absent special circumstances, support for PhD students is guaranteed for five years. Support is extremely limited for students enrolled in the master's degree programs.
The sources of funding in fall and spring semesters include: Teaching Assistantship (TA), Graduate Assistantship (GA, typically a grader), Research Assistantship (RA), and Fellowship (both internal and external). All sources include a tuition waiver. The TA, GA, and internal Fellowship stipends are all identical and more than the university minimum, which increases every year. RA and Fellowship stipends are set by the funding agency. The five-year guarantee includes support from all sources; sources for each student are determined year to year. While receiving financial aid, students cannot have any other employment, and must not enroll in any other degree programs.
Students are eligible for additional summer stipends after the first year, and in a later summer after admission to PhD candidacy. Students are eligible (subject to external agency restrictions) to earn additional money from teaching during Winter or Summer sessions, though there are not always enough assignments for all students who want them.
Students are eligible for a total of $1000 from the department for conference or workshop travel during their studies. The Graduate Office will supplement the amount by another $1000 in many circumstances. See the program's administrative assistant for details. You must apply for the funds well in advance of the travel date. The application form can be found here.