MIAMI — D’Eriq King, the University of Miami’s star quarterback, has spent the off-season anticipating the Hurricanes’ September opener against Alabama. First, though, he is opening for business on Thursday, when college athletes can start to make money off their fame.

Autograph signings and paid appearances could soon dot his calendar. There might be ad campaigns and monetized social media posts, sports camps and videotaped greetings for fans — all of which he hopes will add up to a six-figure income.

“I’m just trying to stay levelheaded,” King said in an interview in his apartment in Miami’s Wynwood district last month, before people and companies could begin to make him offers using a website. “I have a few ideas that I want to do for sure, and then whatever comes later, it comes.”

The changes taking hold on Thursday amount to some of the most consequential shifts in the 115-year history of the N.C.A.A., which has spent generations insisting that students should play only as amateurs and not be compensated beyond the costs of attending college.

The entry of student athletes into a long-forbidden market is expected to collectively steer millions of dollars their way and reshuffle the economic landscape of college sports. It is also rife with challenges, including uncertainty about commercial values, business pitches with caveats and varying quality and certain imbalances to come among teammates.

An even more fundamental riddle is emerging above the individual deals: how to balance sports with school, young adulthood and, now, business.

In locker rooms and group texts, in apartments and over meals, many of America’s college athletes have been strategizing over how to seize opportunities that seemed inconceivable when schools recruited them just a few years ago. Already, players have been publicly floating trademarks and teasing apparel lines.

But the very notion of athletes earning money still unnerves many executives, who are anxious about whether schools will lose marketing dollars. They have fretted over nefarious boosters ignoring rules and launching new pay-to-play schemes, and worried that recruiting and, ultimately, competitions themselves could be compromised.

None of that stopped states like Florida from pressing ahead with laws or executive orders designed to subvert N.C.A.A. policies starting Thursday, the culmination of a groundswell of public pressure.

Just on Wednesday, the N.C.A.A. eased its policies for students and schools elsewhere, a concession that came long after the momentum of state laws had taken hold. The association, rocked by a Supreme Court decision last week that made it more vulnerable to antitrust cases, opted for a largely hands-off approach and will not mete out punishments for players who earn money off their names, images and likenesses.

Gene Smith, an athletic director since 1986 in Division I, the N.C.A.A.’s most prominent tier, said the changes afoot may be the most significant of his career.

“This ecosystem is going to evolve, and we’re going to learn with it, which is, frankly, why I’m comfortable with us taking the guardrails off and tweaking it as we move forward,” said Smith, who is now at Ohio State and views the new system as an opportunity to teach students about the world beyond their campuses.

“We need to see, we need to learn,” he said. “I didn’t know what the heck Cameo was until two years ago.”

Aside from the N.F.L. commissioner, there may be no greater lightning rod in American sports than the N.C.A.A., which enforces rules that about 1,100 colleges and universities set for roughly a half-million student-athletes. Under President Mark Emmert, the N.C.A.A. is often seen as aloof, bureaucratic and prone to self-inflicted crises.

It proved a perilous blend as the college sports industry, which earned about $1 billion from Division I basketball and football in 1985, enjoyed soaring television deals and swelled into a behemoth worth more than $14 billion a year.

Games became glitzier. Coaching salaries exploded. Classrooms sometimes deteriorated as athletic training facilities increasingly resembled palaces. Although the system remained beneficial for many thousands of players seeking degrees, the public perception of the line between college athletes and professionals blurred.

But the N.C.A.A.’s views on compensation — that students could maybe play for tuition, room, board and, in more recent cases, other limited living expenses — remained largely unchanged. The gap between the limits on players and what coaches and administrators commanded brewed discontent that reached the nation’s statehouses, most notably in California in 2019, and Congress.

Democrats framed the issue as one of fundamental economic and human rights. Republicans condemned the N.C.A.A.’s rule book, long a target of litigation, as an unfair restraint on free markets. One state after another passed laws to thwart N.C.A.A. policies. And the association became an even riper target for insiders and critics alike.

“The cheese was being dropped in front of us along the way, and we failed to solve our problem in a way that would placate the courts and legislators,” said Dennis Thomas, the Mid-Eastern Athletic Conference’s longtime commissioner. “So, we’ve ended up where we are.”

He added: “People want to blame one person for it. They want to blame Mark Emmert for it. But we are all complicit in this story.”

As states challenged the N.C.A.A., athletes imagined what their futures might look like if they were able to occasionally earn a few hundred or a few thousand dollars. Along the way, they refined a message that the public increasingly found palatable.

“We’re not getting paid salaries,” said McKenzie Milton, Florida State’s quarterback. “It’s profiting off your name, image and likeness, which is what any other college student can do while being a social media influencer, while going out to work in their communities.”

King grew up the son of a football coach in Texas and first played when he was 4.

He was his high school’s starting quarterback as a freshman. Nebraska, a faded if fabled power, was the first to send him a letter about college. Still, he did not imagine making money anytime soon.

“It’s crazy that it’s here now,” he said, “but if you told me four or five years ago that college players could get paid off their name, I would not believe you.”

He first enrolled at Houston, where he injured his knee but passed for 4,925 yards and 50 touchdowns over four seasons. He transferred to Miami for 2020, when he completed more than 64 percent of his passes and averaged more than 8 yards per throw. Another knee injury set up a difficult off-season.

Still, experts believe he is precisely the kind of player who may do well in the era of name, image and likeness payments: one with wide name recognition, particularly in a place like Miami, who may rise into the professional ranks. Players in other sports could earn some money, but researchers believe the largest sums will typically go to men’s basketball and football players.

Experts also predict that the eased restrictions will be especially beneficial to women, who have relatively few lucrative opportunities in professional sports compared with men but often enjoy large and loyal audiences in their college years.

The state laws and reimagined N.C.A.A. policies set up a buffet of moneymaking options for athletes. Although there are some limits, like a provision that allows Alabama universities to bar players from cutting deals with alcohol companies, players will largely be able to tailor their businesses to their interests. Companies and platforms with Silicon Valley-style sensibilities have emerged to help them navigate the new world, like Dreamfield, which King and Milton have quietly advised for months. They are receiving stakes in the Orlando-based company, whose approach is similar to many others.

Businesses may browse the Dreamfield’s website in search of an athlete to hire for five categories of events, including meet-and-greets, autograph sessions and paid speeches. The rates, set by athletes and currently ranging between $100 and $2,000 an hour, are not negotiable, and the company will generate a contract if a player accepts a proposal.

Dreamfield plans to charge companies or people who hire athletes a 15 percent fee on top of the players’ rates. Later on, Dreamfield will send players, who will be considered independent contractors, paperwork so they may prepare their taxes. (Smith, of Ohio State, said he sometimes jokes with players: “Don’t worry about the N.C.A.A.; worry about the I.R.S.”)

Player after player contends that their sports will still come first. Their talents and fame are, after all, the reason companies might write bigger checks in the future.

“The main focus is playing football and whatever comes after that is a bonus,” said Milton, who is entering his final year as a college athlete. “Something is better than nothing, so we’ll see what some of these guys will be able to do.”

Helped along by his cost of attendance stipend, a recent innovation for college sports, King lives with teammates in a decidedly barren apartment, albeit one with a towering view of Biscayne Bay. He readily concedes his good fortune. He also knows how much money is flowing in and out of big-time college athletic departments. (Miami is a private university, but federal records suggest its athletic department had more than $115 million in revenues between June 2019 and May 2020. Its football program was credited with $59.4 million in revenue during that period.)

“We see schools making $50, $60 million off the backs of athletes,” he said. “I’m grateful for my scholarship. I’m grateful to the University of Miami and the school I went to. But that’s not equivalent to a scholarship, $60 million.”

Still, Miami, which hosted the signing ceremony for Florida’s law last year, has been among the most aggressive schools to champion name, image and likeness changes publicly. In December, the school said it had signed a deal with INFLCR, which works with many schools, to help students understand the opportunities ahead. At the time, Manny Diaz, the football coach, lauded the deal as a way for players to “build your brand in the heart of one of the world’s most dynamic cities.”

Before this week’s opening, King attended personal finance classes offered by the university on Wednesdays to sort through myriad issues. He enlisted his mother and brother to help him assess whatever offers may arrive, sketched out ambitions for a podcast and considered the kinds of activities that held the most interest. Autograph signings and speaking engagements, he suggested, were his favorite.

With summer football obligations done around the lunch hour, he said, there were still plenty of hours in the day to pick up the kinds of gigs that athletes have never had.

He said he planned to save much of his earnings, and perhaps send some back home to Texas, as he looks toward life after his final season at Miami. He said he did not immediately plan to trade in his Jeep Wrangler for one of the glittering imports that fill South Florida’s highways.

But as Thursday approached, he said he was eager to at last earn some of what he sees as rightfully his. For too long, he and other players said, the system had worked for many — but not always for them.

“In some sense, you could say we got taken advantage of,” he said. “I think a lot of people, they just see us on Saturdays, and that’s the problem. If they had seen what we do every single day, day in and day out, then they’ll understand why it’s such a big deal to us to get paid.”