It is, of course, important to note that I didn't pay for either of them That's the discriminant, right there. If they pay you it's because they need someone

It is, of course, important to note that I didn't pay for either of them That's the discriminant, right there. If they pay you it's because they need someone to get some work done, and the funds to pay you come from someone willing to pay them - NSF, NIH, industrial sponsor, whatever. But if you pay them they'll just make some advanced undergrad courses a requirement for your masters, and it's a farce throughout.