Whilst some students are very poor a lot of them aren't in my experience, many are generously supported by their parents, run cars, have pcs and all the latest gadgets, phones, trust funds coming their way.
Fees, loans, credit cards, over drafts etc are paid back after graduating, and I would hazard a guess that's when most would start wanting to earn a few extra pounds.
Many ladies probably also use sex work to fund further education as mature students, yet for some reason everyone wants to speak to the stereotypical straight from school, 'poor' student.