The offers of financial aid depend on several factors including GRE/TOEFL scores, personal/phone interviews, previous research/industrial/teaching experience, area of concentration, department needs and the financial factors. Competition for teaching and research assistantships is always very keen and admitted students are always encouraged to find other sources of support including personal/family funds. Several students start their graduate education based on personal funds and later find some form of financial support including assistantships and on-campus employment though clearly, it can not be guaranteed.
There are no set minimum requirements. The offers of graduate admission depend on several factors including previous coursework and performance therein, previous research/industrial experience, GRE/TOEFL scores, recommendation letters, area of concentration and the department needs. You may apply to either the MS or the PhD program though requirements for admission to the latter are obviously much higher.
TOEFL scores are valid for 2 years from the date you take the test. If your GRE scores are more than 2 years old, see if you can get an official score report (directly from ETS) to include with your application packet.
For international applicants, TOEFL and GRE scores are required for admission into our graduate programs. For domestic students, GRE scores are welcome (in fact, recommended) though not required and will be considered in the admission process if submitted.