Making a living" and "economics
The specific topic is the consumer culture of typical college students. That is, consider the types of things that college students typically need and want in order to live like a typical college student, and then where they buy them and for how much--everything from food to electronics. So your creating a portrait of how college students live through the types of things that they typically purchase. You can present it as an essay about a day or weekend spent shopping for goods, what places they're purchased from and what kinds of prices they would pay for them. You can also state to what extent these are things that students need these things, want these things without really needing them, and why (for example, just because everyone else has these things and they want to fit in). So this can all be based on your observations of other college students if not your own purchase habits.
So you'd write this up as a two page typed essay.