When I was a teaching assistant in university in Singapore here I knew a guy that ran the same sort of business, albeit for coding assignments instead of essays. He was making a couple of thousand a month - showed me the bank records and everything.

I'll admit, only reason why I didn't sign up was because I was already swamped and sorta lazy - we're talking about like a hundred bucks for something as trite as the first assignment for CS101. Apparently the most generous clients were Chinese students with more money than drive.