"I own your cum" or "Your cum is mine"

[RustedSage]

The perspective of the story is from a boy who recently graduated high school and is waiting before going to college. He moves in with his sister and her roommate who are broke nursing students. The story starts off with him talking about how his cock grew a lot recently and his good it feels to cum. He mentions liking to surf and bum around, but gets paid to donate his sperm. He makes $150 a donation and donates 3 times a week but he has to not cum 24 hours before the donation or they pay half. His sister's friend and roommate gets jealous that he makes $450 a week "just jerking off" which leads her to seduce him.