By the way, the position of "graduate assistant coach" is distinctly different from the one discussed above. In that case, a student (usually a former player who is either working toward completing his ungrad degree or taking graduate courses) serves as a part-time, uncompensated coach. His funding sources tend to come from those traditionally tapped by other students.
As an example of this, it was announced last week that one of my son's former college teammates has returned in this capacity to complete his undergrad degree after playing professional baseball. As a result, that team will field a total of 5 coaches this season (Head Coach, Hitting Coach, Pitching Coach, Assistant Coach, and Graduate Assistant Coach).
Some graduate assistant coaches go on to become paid college baseball assistants, while others use the college degree they've earned in other fields.