I interpreted it as a deal/con on Quinn's part. I think Quinn has a deal with Burke where he basically "cooks the books" to give free tuition to her girls in exchange for their services. The money the girls bring in from other clients, Quinn takes and tells them that money is how she's paying their tuition, when it's actually just for Quinn, probably to help fund the drug business she's also running.
The fact that, through all of this, Quinn never seems to have enough money means she's not turning any actual profit off her scheme(s), which just points to Riona being right all along: Quinn's not as smart as she thinks she is.