American Olympians are just weeks away from representing their country in London, but many will return home -- medals won or lost -- to face significant financial challenges.

Unlike athletes in many other countries, American Olympians receive no direct support from the federal government.

And the U.S. Olympic Committee, with a $170 million annual operating budget spread across all sports, offers health insurance and stipends to only a limited number of competitors.

Athletes, without government support, are instead forced to cobble together an income made up of prize money, apparel contracts, grants and part-time work.

Only 50 percent of American track and field athletes who are ranked in the top 10 in the nation in their event earn more than $15,000 a year in income from the sport, according to a survey conducted by the USA Track and Field Foundation.

And most athletes not ranked in the top 10 nationally fare much worse.

"There is an incredibly steep drop in earning power from the elite of the elite athletes to individuals who are just slightly lower ranked," said Jack Wickens, who conducted the survey and oversees the foundation's grant program.

Adding to the uncertainty, most apparel contracts signed by track and field athletes contain provisions that result in sharply lower income if an athlete is injured or fails to perform as expected.

How much am I worth?

Adam Nelson, a two-time silver medalist at the Olympic Games, has seen both sides of the divide, having climbed to the top of his event -- the shot put -- after graduating from Dartmouth College.

Nelson said the viewing public is generally unaware of the financial sacrifices made by athletes.

"If you don't perform on the couple of days that matter, you will lose almost every opportunity to make money in this sport -- and it will happen very quickly," Nelson said.

Nelson, who also has a graduate degree in business from the University of Virginia, has gone to near-ridiculous lengths to support his wife and two children, including a scheme that involved auctioning off a sponsorship on eBay.

"Apparently I am worth $12,000 for a month," Nelson said, referencing the winning bid from MedivoxRx. The creative approach was needed, Nelson said, after a sponsor dropped his contract immediately after he won his second silver medal at the 2004 Summer Games in Athens.

"My thought was that if someone could auction a piece of toast with Jesus on it for thousands (of dollars), that I could auction myself for a similar amount," said Nelson, now happily sponsored by apparel-maker Saucony.

Nelson, who also has five world championship medals to his name, said that athletes who compete in the shot put face additional financial pressures, as the event is far from the limelight.

Performance-based pay

Brian Sell, an an Olympic runner who made the U.S. team for the 2008 Beijing games, should have had an easier time. He competed in the marathon -- one of the sport's biggest attractions, and one that has big money available at races like New York, Boston and London.

But Sell, who made 50 percent of his income from performance-based prizes at his peak, said that it took him years to make any real money in the sport.

During a particularly lean period, before he joined a team of athletes sponsored by apparel-maker Brooks, Sell's income was below $25,000 for three consecutive years.

"It's a small percentage of people who make a real living in this sport," Sell said. "And if you didn't run well, you didn't get paid."

To illustrate just how precarious major payday events can be, Sell pointed to his run at the Boston Marathon, where he ran 26.2 consecutive miles at under 5:00 per mile pace, to capture fourth place and a check for $25,000.

"That's more than I sometimes made in a year," Sell said. "And if I were injured, that's a big old goose egg."

With a string of successes, Sell's income rose to $125,000.

"It was amazing," the marathoner said. "I went MC Hammer-style for a while there and bought two or three motorcycles and a new truck."