For Burke to proposition a single student, let alone multiple students, could easily be career suicide. Quinn is his conduit to girls who are already primed for him.
Also, I also don't think Burke is actually paying for their tuition. He's just setting up fake scholarships and fiddling the books. It's certainly not worth it to pay the 10s if not 100s of thousands for each degree for the privilege to fuck each of these skanks (to be fair, my mc is a skank too).
On that note, these girls are seriously fucking loose. I don't really know what Burke's angle even is. He may as well legitimately pay for prostitutes, at least a professional prostitute would adhere to strict hygiene standards, these girls... not so much.