Irish boxer Darren O'Neill quit his job teaching at Holy Trinity Primary School in Dublin to train full-time for the Olympics and isn't sure he'll get the job back when he goes home.
He also had to give up hurling, a rough-and-tumble native Irish sport that combines elements of field hockey, rugby and soccer. It is dominant in his hometown, hurling-mad Kilkenny.
"I enjoyed the teaching as a release from boxing, too, and took a risk in leaving," he said. "It was a tough decision, same as leaving the hurling, but boxing gave me more personal satisfaction."
O'Neill lost last week in his second bout, to Stefan Hartel of Germany, but he'll go back to find a hand-painted banner on the school roof that says "GOOD LUCK MR. O'NEILL."
Lance Brooks, an American discus thrower, worked as a bouncer and bartender and what's known as a barbacker restocking the cooler and taking out the trash when he moved to Denver five years ago and started to train.
He also worked Colorado Rockies baseball games, coached at a local high school, worked at an oil-change service and did construction all before his coach told him to cut out some of the jobs or lose his trainer.
Kai Jahnssan, a pistol shooter, serves in Finland's Coast Guard Air Flight Patrol as a helicopter rescue swimmer. Another marksman has a job more suited to his Olympic discipline: Italy's Luca Tesconi, who won the silver in 10-meter air pistol, is a police officer in Tuscany.
Mark Adams, a spokesman for the International Olympic Committee, said the IOC distributes more than 90 percent of its revenue from TV rights and sponsorship deals to national Olympic committees, in part to ease the burden on athletes.
The IOC has its own program, Solidarity, that provides training, equipment and travel money for particularly needy athletes.
"We have a responsibility to balance an elite games with sport for all," Adams said. "We try to make it as level a playing field as possible."
That is more possible when national Olympic committees and sport federations receive government money.
When they don't, or when there isn't enough money to go around, athletes have little choice but to go it alone eking out a living and scrambling for sponsorship deals when they can get them.
That includes the United States. The U.S. Olympic Committee is a nonprofit that gets no help from the federal government.
Nick Symmonds, a four-time U.S. outdoor track champion in the 800-meter, auctioned a spot on his shoulder on eBay for $11,100 for a temporary tattoo with the name of the highest bidder.
Hanson Dodge Creative, a marketing firm that focuses on "active lifestyle" consumers, made the winning bid, but Symmonds had to cover the shoulder because of IOC rules preventing athletes from hawking their brands during the Olympics.
Wendy Houvenaghel is a dentist in Northern Ireland when she's not riding for Britain in track cycling's team pursuit. While she wasn't practicing dentistry in the run-up to London, she had to take continuing education courses to keep her license valid, and plans to pick up the profession full-time once the Olympics, and her cycling career, are over.
"It's something I feel is important, looking beyond the Olympic Games," she said.
It's also a profession that comes in handy when the team is on the road and teammates develop what she delicately calls "wisdom tooth situations."
Japanese equestrian rider Kenki Sato has one of the more unusual full-time jobs: He's a monk at his family's Buddhist temple near Nagano, the site of the 1998 Winter Games. Sato acknowledged he was probably the only Olympian with such a profession, but said the discipline of his day job he sometimes spends 19 hours a day sitting and meditating helps him while he's riding.
"Before the competition starts, I concentrate," he said. "I'm behaving more like a monk," he said.
U.S. swimmer Tyler Clary went back to work as soon as he won a gold medal and set an Olympic record in the 200-meter backstroke. He's an accomplished DJ, and headlined at a London club called Chinawhite last weekend though he said the gig wasn't so much work as "part of the celebration."
But of all the extracurricular jobs among the 2012 crop of Olympians, perhaps Logan Campbell's raised the most eyebrows. The New Zealand taekwondo fighter opened a high-end brothel in 2009 in Auckland to finance his training and travel schedule ahead of the Olympics, so his family wouldn't have to bear the burden. Prostitution is legal in New Zealand.
"At the time, taekwondo wasn't getting any funding at all," Campbell said earlier this year. "So it was pretty much to get good at the sport, you had to get international competition, and there wasn't any funding for us."
Campbell, who competes Thursday, sold the brothel in 2010 after he was criticized by Taekwondo New Zealand and the national Olympic committee and, more importantly, after sponsors started funding the sport.