There are some two revenue streams that college radio stations rely on.
The first revenue stream that college radio stations rely on is that which comes from their parent college sponsorships. You have to keep it in mind that some of these radio stations, actually majority of these radio stations, are typically affiliated to the faculties that teach things like broadcasting and communication studies in their respective colleges. They therefore tend to get some funding from the colleges, out of awareness for the fact that they are, in actual fact, teaching aids of sorts. Actually, some colleges opt to fund their radio stations in this way entirely: meaning that the college radio stations are entirely dependent on this particular revenue stream.
The second revenue stream that college radio stations rely on is that which comes from advertising. There are many advertisers who endeavor to have their ads run on college radio stations. They do this for a very specific reason. They realize that the college students are people who, after making applications at www.fafsa.ed.gov get some money, in the form of the so-called myedaccount loans, and that is money they can be persuaded to spend through the advertisements in question. This pushes them to pay for advertising spots in college radio stations, if they are given that chance.