Joint stands to more than double her career earnings after holding her nerve to clinch a tension-filled 6-4 7-5 victory over experienced German Laura Siegemund.
But confusion reigns, even among tennis officials, over precisely how much of the $US140,000 ($A207,000) prize money Joint is entitled to, given the 18-year-old is committed to starting a psychology degree at the University of Texas.
NCAA rules in the US state: "In tennis, prior to full-time collegiate enrolment, an individual may accept up to $10,000 per calendar year in prize money based on his or her place finish or performance in open athletics events (events that are not invitation only).
"Once the individual has reached the $10,000 limit in a particular year, he or she may receive additional prize money on a per-event basis, provided such prize money does not exceed the individual's actual and necessary expenses for participation in the event."
Joint, though, begs to differ.
"It's different rules for college," she said on Monday while savouring the most significant win of her fledgling career.
"(As) student athletes, you can take the money from the tournament but you have to, like, make expenses until the end of the year.
"So it's different from amateur to college."
🇦🇺 Maya Joint, the third-youngest woman in the draw, wins her Grand Slam debut! pic.twitter.com/pnORDC6FKl— US Open Tennis (@usopen) August 26, 2024
Several former players, including good friend and confidante Reese Brantmeier are legally challenging the ruling.
"It's very complicated," Joint said.
"My mum looks at it and then the Texas Compliance Office helps me with all that."
Come what may, Joint is steadfast in her plan to continue studying.
"I'm still going after this tournament," she said.
"I think I'm going to go to Austin. My class has actually started today.
"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).
"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."
The Michigan-born talent was eligible to represent Australia courtesy of her father Michael and switched allegiances last year, and credits both her parents with having passed down special sporting pedigree.
"My dad's from Melbourne. He was a professional squash player," Joint said.
"My mum (Katja) is German. She played tennis when she was younger and squash and badminton, so we come from a racquet family for sure."
Set to soar to a career-high No.107 in the world following her inspired run from qualifying, Joint will gatecrash the top 100 if she can upset former Flushing Meadows finalist Madison Keys in the next round.
"I have no pressure," she said.
"I've seen Madison Keys play multiple times on television but obviously never played against her.
"So I'm excited."
And if she does receive all her US Open prize money in full?
"It's crazy. I've never had (that)," Joint said.
"I don't really know what to do with it."
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