At 16, Thalheimer and a buddy had all but cornered the market on lawn-mowing jobs in his suburban Philadelphia neighborhood. They had 200 lawns and a crew of kids working for them and were clearing close to $250 each week. Big money for a couple of minors in the mid-1970s.
By the time he graduated high school and headed off to Temple University, Thalheimer had $15,000 in the bank.
Then he discovered the stock market.
Within a couple of years Thalheimer was sitting on a $50,000 portfolio of mainly blue chip stocks. But that wasn't enough. He wanted to score big and be riding on easy street before the ink was dry on his college diploma.
So Thalheimer started investing on the margin. Selling short. Placing naked puts. He got burned, badly burned. He lost all his money - and then $30,000 more.
"I knew that you could lose what you had. I didn't realize you could lose more than you had," he said. "I really screwed up, believing my own omniscience, thinking I could do no wrong."
That painful lesson still lingers, but it hasn't stopped Thalheimer, 49, from rolling the dice a few more times in a career that has included a stint as an orderly at a psychiatric hospital, more than a decade in San Diego city government, a flight-training business and a run for political office.
He will be the first to tell you that he's made a few decisions that seem, in retrospect, as ill-advised as his stock market gamble. But he's managed to overcome them, thanks in large part to a motor that never seems to stop and an inner toughness he says comes from growing up as the son of a father who fled the Holocaust and a mother who survived an Italian internment camp.
No venture illustrates these qualities more than San Diego Flight Training International, a flight school that Thalheimer and Rick Morrison operate on Montgomery Field. Since 1989, the two have prevailed despite an early lack of funding, an initial business plan that Thalheimer describes as "flawed" and 9/11.
Today, the school, with 17 planes, 17 employees and $2.5 million in annual revenue, is considered in the top tier nationwide. It welcomes the recreational pilot, but its main focus is the fledgling professional pilot - the person who dreams of someday flying a 747.
"(Flight training) is a difficult business because everyone in aviation wants to do it," said John King, a San Diego-based supplier of flight-training equipment. "They succeed because they are so focused on quality."
Big, bald-headed and well-dressed, Thalheimer is the face of San Diego Flight Training - the guy who takes the meetings, deals with the public and rallies the troops. Morrison, a former Navy aviator, likes to stay in the background, keeping an eye on the planes and supervising the training.
"Phil is a visible kind of guy, a born politician," Morrison said. "He loves that stuff. If there is a camera around, Phil's gonna be in front of it."
Thalheimer has been in the spotlight plenty in recent years. Although a devout Jew, he was involved in the fight to preserve the Mount Soledad cross. And he was chairman of Southern Californians for Jessica's Law; the law, which puts limits on sex offenders, is being challenged in court.
Thalheimer, a Republican, pushed San Diego City Councilman Scott Peters to a runoff in the 2004 election for the District 1 council seat.
His brother Jeffrey Thalheimer said Phil was always more involved outside the house than his two younger brothers - and very ardent in his beliefs.
"He was never an 'on the fence, take it or leave it' kind of guy," Jeffrey Thalheimer said. "He would believe in something and believe in it quite passionately from the very beginning."
Thalheimer doesn't come from a family of flashy political types.
His father, Hans Thalheimer, was born in Tubingen, Germany. His family left Germany for Yugoslavia in 1936 after his grandfather, a World War I war hero, read Adolf Hitler's "Mein Kampf."
In 1939, the family fled to America with the help of two of Thalheimer's great-uncles. Once in America, Hans Thalheimer joined the U.S. military and fought the Nazis.
Phil Thalheimer's mother, Nelly B. Thalheimer, who grew up in Yugoslavia, wasn't as lucky. Her family was still in Belgrade when the Axis armies invaded, and the family was taken prisoner by the Italians.
Nelly Thalheimer spent most of the war years in an Italian internment camp on the island of Korcula in the Adriatic Sea. In late 1943, she was among 1,000 refugees allowed into the United States and spent the rest of the war in a refugee camp in Oswego, N.Y.
Hans and Nelly, who met in a synagogue youth group, ended up settling in Philadelphia, where they enjoyed a relatively prosperous but quiet life. Hans ran the family scrap metal business, and Nelly was a homemaker.
Phil Thalheimer describes his father as a cautious, risk-averse businessman who favored a slow and steady approach to building wealth.
"I'm more of a risk-taker than anyone in my family," he said. "My parents have often shaken their heads in disbelief at the things I've done."
Yet Thalheimer says he owes much of his success in business to his father, who instilled in him an uncommon work ethic and a tough but compassionate management style.
"My father's philosophy is to let people swim, sink, but never drown," he said. "If you stay under water for more than a couple seconds, he's jumping in. That is the core of my management belief."
After the stock market debacle, Thalheimer, who'd earned a bachelor's degree in psychology, bounced around for a while. He eventually signed on as an orderly in a suburban Philadelphia psychiatric hospital's adolescent unit.
In addition to the hours, which did not mesh with his early-riser mentality, Thalheimer had a hard time relating to the youth there.
After two years, the clinical director of the hospital took Thalheimer aside, told him he was not empathetic enough and suggested he go into industrial psychology.
So in 1983, Thalheimer moved to San Diego and enrolled in the California School of Professional Psychology, which is now part of Alliant International University. He earned a master's degree and in 1986 landed a job in the city of San Diego's organizational effectiveness program.
He worked for the city for a decade and rose through the ranks to the position of deputy director. Then he went to work as a manager for San Diego Data Processing Corp., a city-owned nonprofit that provides data processing and telephone service to the city and other government agencies.
Thalheimer enjoyed his work with the city but knew all along that at some point he would strike out on his own.
"I never liked working for other people," he said. "As much time as I spent in local government, I never felt like I fit."
In 1986, Morrison, who had left the Navy for a career in consulting, was advertising his services as a flight instructor in a local newspaper.
He got a call from Thalheimer, who wasn't the easiest of students.
"He was a tough nut to crack," Morrison said. "To fly airplanes you have to be a good multitasker and mechanically inclined. Phil wasn't a real mechanical kind of guy, but one thing he didn't lack was the drive and desire to finish."
The two became close friends, and in 1989 they scraped together every spare nickel for a down payment on a $225,000 flight simulator. The original idea was to simply rent some space near Montgomery Field and make the simulator available to all comers.
"They'd pay by the hour and the money would just roll in," Thalheimer quipped. "And we'd be on the beach eating bonbons."
They discovered that people won't keep renting time in a simulator if they can't follow up with time in a real plane. Their product only met half the need.
"If we would have thought about it for more than 15 minutes, we would have realized that in the beginning," Thalheimer said. "But in the euphoria of our brilliant idea, it didn't occur to us."
Red ink was flowing heavily by 1990, and the partners knew they had to either shut down or invest in planes. They chose the latter and for the next decade worked around the clock to establish themselves.
A few years later they had 12 planes and were slowly growing their business, especially in the international market. But Thalheimer didn't quit his day job until 2000, just 18 months before the Sept. 11 attacks.
By 11 a.m. on that morning, the government had grounded all civilian aircraft and established a San Diego connection to the terror plot. At 2 p.m., three FBI agents showed up in Thalheimer's office with a contact sheet of pictures of all 19 hijackers.
"They asked me if I recognized any of the faces," he said. "I had this unbelievable fear: What if they trained with us? There would have been no way of knowing."
As it turned out, none of the terrorists had trained at San Diego Flight Training. But because of the federal flight restrictions and the fear that followed the attacks, the company had essentially no revenue stream for two months. The international business - the company's bread and butter - was done for the foreseeable future.
"I'm scared. I'm really scared," Thalheimer remembered. "I'm looking longingly at my steady paycheck from the city of San Diego and thinking I left at an inopportune time. But the idea of bankruptcy was not something I was willing to entertain."
The best course of action, the two decided, was another gutsy move.
With the international market gone, they had to gear their entire business for the domestic market. Because of the huge number of flight training schools nationwide, the focus on quality meant investing in new equipment and raising prices when things were at their worst.
Six years later San Diego Flight Training is a certified Cessna Pilot Center, which puts it at the very top among schools nationwide. And consistent revenue growth has become the norm.
"Was it gutsy? Yes," Thalheimer said. "But when you have two choices, and one isn't going to work, the other one is easy."