SAN FRANCISCO (AP) — Professional athletes frequently get traded to other teams, but San Francisco 49ers tight end Vernon Davis is about to be the first ever to be traded like a stock.

Davis, an eight-year veteran of the National Football League, is serving as the litmus test for a risky concept: Whether sports stars should be treated like public companies, whose moneymaking potential can be bought and sold on an exchange by ordinary investors. San Francisco-based Fantex Inc. plans to operate the exchange and will orchestrate Davis’ initial public offering of stock after getting regulatory approval from the Securities and Exchange Commission.

The deal requires Fantex to pay Davis $4 million in exchange for 10 percent of his future earnings, including some of his off-field income. To cover Davis’ fee, Fantex seeks to sell 421,100 shares of stock at $10 apiece. The company hopes to complete the initial public offering in the next few weeks.

Davis, 30, will need to make more than $40 million just to deliver a small return on Fantex’s investment in him.

Fantex is counting on him to earn most of that money after his current contract with the 49ers expires in 2015. By then, Davis will be at an age when it might be difficult for him to land another big payday, although there are precedents for it. That means the deal could prove to be more profitable for Davis than the investors who buy the Fantex stock tracking his performance.

IPO expert Francis Gaskins is advising investors to stay on the sidelines. Fantex’s concept “just sounds like something that P.T. Barnum would try to sell,” says Gaskins, president of IPOdesktop.com. “I don’t think it’s going to work out.”

Fantex CEO Buck French has been trying to overcome skepticism while traveling around the country for pre-IPO meetings that began in early February. The journey included traveling to 12 cities in two weeks last month on an old bus that retired NFL announcer John Madden used to ride to get to his broadcasting assignments.

“We are successful businessman and we are putting together a transaction we believe in,” French says.

Fantex will cover its expenses by taking a small cut of the revenue generated by Davis. Investors who own the Davis tracking stock could profit from a combination of the player’s earnings and gains in the value of their shares.

The income will come from Davis’ career football earnings dating back to last October, as well as any money he makes from off-the-field endorsements or other jobs, such as sports broadcasting, that he gets during the rest of his life.

The deal only covers earnings tied to his success as an athlete. If Davis decides to do something like sell insurance after his playing days are over, Fantex won’t receive any of that money. His income from his holdings in a Jamba Juice franchise and a San Jose, Calif. art gallery is already excluded.

The Fantex IPO is part of “a land rush to see who can come up with the next clever concept to bring fans closer to the game,” says veteran sports agent Leigh Steinberg, who has represented hundreds of NFL players during his career. “It’s a manifestation of the different ancillary revenue flows that players, speculators and investors can engage in, all of which is created by the love of sports.”

Fantex is focusing on players in a lower-income bracket. Besides Davis, the company also has lined up IPOs tied to Houston Texans running back Arian Foster and Buffalo Bills quarterback EJ Manuel. None of them have a contract that will pay more than $6.5 million next year. Fantex hopes to eventually sign similar IPO deals with other athletes outside of football.

Athletes who sign deals with Fantex get a guaranteed payment upfront and promises of help managing their personal brands for years to come. Some of the guidance may be provided by NFL Hall of Fame quarterback John Elway, a director on Fantex’s holding company, and retired golf star Jack Nicklaus, who is a Fantex adviser.

Davis isn’t discussing his reasons for participating in the IPO yet because of securities regulations discouraging public comments that could sway investors considering whether to buy newly issued stock. He is normally outspoken and has a wide range of interests outside football. Besides his art gallery and Jamba Juice franchise, Davis is such a big fan of curling that he served as honorary captain of the USA’s team during last month’s Winter Olympics.