The Michigan-born Joint, who has committed to a psychology degree at the University of Texas, beat German Laura Siegemund 6-4, 7-5 in the opening round of the US Open on Monday.
National Collegiate Athletic Association (NCAA) rules state that prior to full-time collegiate enrolment, players can accept prize money not exceeding $10,000 per year and additional prize money should not exceed "actual and necessary expenses."
"It's different rules for college," Joint told Australian media after booking a clash with American Madison Keys.
"As student-athletes, you can take the money from the tournament but you have to make expenses until the end of the year. So it's different from amateur to college."
Joint's friend and fellow player Reese Brantmeier is among several athletes who had sued the NCAA in North Carolina federal court in March over the prize money issue.
"It's very complicated," said Joint, who decided last year to represent the country her father hails from.
"My mum looks at it and then the Texas Compliance Office helps me with all that."
Despite missing the start of her course, Joint said she was determined to go to college after the tournament.
"I decided a long time ago that I wanted to go to college and I wasn't really expecting to get this far (in tennis)," said Joint, who is expected to reach a career-high world number 107 after her run from qualifying.
"If I go to college, then I get my scholarship spot. If I decide to go pro in the meantime, I can always come back on scholarship, which is a big deal."