Really, a quick forum search would have yielded:
Oncampus/Off-campus Jobs On Campus Jobs v Off Campus Jobs Employment Opportunities On Campus? becoming a ta Work Study vs. Real Job? Question about Work Study Internships at Columbia
...and of course, for a broader perspective:
What do u like and hate about Columbia?
Really, the best money to be made while you're in school is with freelancing. Tutoring, translation, and tech work all pay very well and have plenty of willing clients in the city.