Jeff Gross / Getty Images Houston Texans running back Arian Foster at Candlestick Park on October 6, 2013 in San Francisco, California.

For your fantasy team, star Houston Texas running back Arian Foster is one of the safest bets out there — though he’s only scored one touchdown yet this year, to the disappointment of many fantasy owners.

But if you’re going to buy actual stock in the guy, proceed with caution. Lots of caution.

On Thursday a company called Fantex announced an intriguing new business plan: an athlete stock exchange, with real money involved, with Foster as the first offering. Fantex is offering 1,055,000 shares of “Fantax Series Arian Foster Convertible Tracking Stock” for $10 per share in an IPO; according to Fantex, investors can start placing orders in two weeks. No individual can buy more than 1% of the shares, which amounts to $105,500. Foster gets $10 million in proceeds: the remaining $550,000 pays for underwriters and other expenses. In exchange for this $10 million, Foster must fork over 20% of his future earnings, from football and off-field income like endorsements, merchandising, coaching and football camps, even movie appearances (if Foster plays himself or the role of a professional or amateur football player).

“You can see how it makes sense for Arian Foster,” says Craig Pirrong, finance professor at the University of Houston’s Bauer School of Business. Foster is hedging. He’s already in his fifth year: the average NFL career lasts 3.5 years, and according to prior research, running backs have even shorter careers. No player takes more of a pounding than the primary ball-carrier. And NFL contracts aren’t fully guaranteed.

The $10,000,000 is like an insurance claim. The price for this windfall: a 20% tax on future earnings. Assuming Foster remains healthy, and is able to capitalize on his fame when his career does end, this tax should provide a healthy cash flow to Fantex. “Arian still owns 80%, so he’s very much incentivized to continue to build his brand,” says Buck French, co-founder and chief executive of Fantex. “And by the way, we’re incentivized to help him, because we have 20%. That was our whole idea of starting this company, aligning everyone’s incentives properly.”

(MORE: Abnormal Brain Activity Found In Retired NFL Players)

But what about the individual investors actually buying the Foster stock, and financing Foster’s payment? They are, in effect, insuring Foster, without guarantees of a premium payment. If you buy a Foster share, there are two ways you can make money. One is through dividends. Fantex can choose to return some of the 20% of those future earnings over the common stock investors. “We absolutely have an expectation to pay out a dividend,” says French. Dividends, however, are never guaranteed. “The company has tremendous discretion in how to allocate the cash flows it gets from its 20% of Foster’s earnings,” says Pirrong. And Foster could get injured tomorrow — remember, he’s an NFL running back. His future endorsements and commercial opportunities can dry up. That 20% of future earnings may be a small pie for investors.

As outlined in the prospectus filed with the SEC, Fantex’s parent company will hold 99% of the voting power of the outstanding common stock. You are not buying equity in Arian Foster: Foster can run his career however he wants to. You’re in essence buying shares in Fantex, a company whose only revenue, right now, is 20% of Foster’s future earning.

The other way you can make money is to trade Foster shares on an exchange that Fantex will operate. “This is linked to real cash flows associated with a professional athlete,” says French. True, but Foster’s excellent performance — and compensation — doesn’t automatically boost the stock price. In sports gambling, if you bet on a team, and that team covers the spread, you get a guaranteed payout. Even in fantasy football, if Arian Foster rushes for lots of yards and touchdowns, you accrue points, which could help you win your league’s pot. You directly benefit from Foster’s success. Here, even if Foster breaks every rushing record out there, and does more commercials than Peyton Manning, there’s still no guarantee his stock price will rise. “The market price of our tracking series may not reflect the intrinsic value or performance of the associated tracking series brand,” Fantex writes in its SEC filing.

Pirrong cites two factors that could put downward pressure on Foster’s stock price. First is liquidity risk. This is a brand new market; there’s little assurance that enough investors will want to jump in, and take shares off anyone’s hands. The second is the nature of the investment. Since the shares don’t give you any direct ownership or say in Foster’s decisions, they may trade at a discount.

To its credit, Fantex lays out all the various risks, loud and clear, in its SEC filing. “This offering is highly speculative and the securities involve a high degree of risk,” the company writes. “Investing in our Fantex Series Arian Foster should be considered only by persons who can afford the loss of their entire investment.” Brian Goff, economics professor at Western Kentucky University’s Ford School of Business, likens the Foster investment to a junk bond. “That’s not as pejorative as some might take it,” Goff says. “Most high-yield bonds do not default, but the level of risk and uncertainty is high.”

Pirrong spent part of Friday reading through the filing. “It has a penny stock feel to it,” he says. “Very much so.”

(MORE: The Jadeveon Clowney Dilemma: College Sports Can Be A Lousy Game Show)