NEW YORK (CNN/Money) - When Ryan Thompson was fifteen years old, his dad made him an enticing offer. If he saved $2,000 in an IRA that year, he could have the 1987 Mustang that was in the garage.

Thompson, who has a passion for cars, saved the money he made doing lawn work and earned the prized set of wheels. But after counting his coins all year, he realized he had a new passion: watching his money grow. He's since contributed the maximum amount to his IRA every year, which now holds about $14,000.

"My Dad, who's a big fan of saving and investing as well, told me that if I started maxing out an IRA, I'd have more than any of my friends had, and of course, now I do," Thompson said.

When it comes to bringing home a paycheck, Thompson is no slouch. During the week, he's an RA (residential administrator) at his school, Miami University, in Oxford, Ohio. That brings in about $3,500 a year. During the summer and on the weekends, he runs his own landscaping business, Ryan Lawn & Landscape, which pulls in about $30,000 a year, pre-tax.

Thompson, who's majoring in organizational leadership and management, gets to use his classroom skills on the job: his company now employs two of his friends and his younger brother, Nathan.

"I got my first lawn in the sixth grade. Now we have about 32 customers, and we do everything related to lawns and landscaping -- mowing, mulching, fertilizing, pruning, even landscape design," Thompson explained.

He bills customers on a monthly basis, and Thompson saves those earnings into various accounts, including his Vanguard IRA portfolio, a taxable Vanguard 500 mutual fund, now worth about $4,000, a Vanguard Health Care Fund, which totals about $3,000, and two savings accounts, which have about $5,300 spread between them. He also has about $1,600 in shares of Home Depot, kept in an Ameritrade account.

But Thompson keeps the vast majority of his life savings - just over $50,000 - in bank certificates of deposit, or CDs. He says that choice reflects his investing style, which is to keep things very conservative.

"I recently sold positions in both Cisco and AOL Time Warner," he said. "I would rather see my money grow steadily over time, rather than in short bursts. With my investments, I should be able to do whatever I want by the time I'm 55."

In spite of the success he's had, Thomspon said he doesn't plan on making landscape work his full-time career. After graduating in December, he hopes to find a job in the Cincinnati area at a medium-to-large company, like Procter & Gamble or Messer Construction Co.

"I would love to move up the ladder and prove myself as a manager," he said.

Thompson estimates he'll be able to save about $25,000 a year following graduation, siphoning $22,000 into taxable accounts and $3,000 into his Roth every year.

Based on these estimates (and the assumption he'll stick with a conservative portfolio - bringing in, say, an annualized 4 percent rate of return), Thompson will have a cool million when he's 44. On the other hand, if his portfolio earned about 9 percent a year, he'd be on track to hit the million-dollar mark by his 37th birthday, according to CNN/Money's Millionaire Calculator.

In the future, he also hopes that he'll be able to afford "a beautiful house in the woods" where he can relax and keep a few more nice cars.

"I'm into the car thing," he said. "Besides that, I like to run and work out. And I work a lot."