BUSINESSWEEK ONLINE : SEPTEMBER 25, 2000 ISSUE BUSINESSWEEK INVESTOR Who Wants to Be a Teen Millionaire? Television viewers may dream of becoming millionaires. But David Leung is already halfway there. And he's only 17. The Massachusetts Institute of Technology freshman's wealth comes not from a get-rich-quick scheme or his parents, but from seven years of investing. The Palos Verdes Estates (Calif.) resident started at age 10, when his parents gave him $7,000 in Microsoft stock for winning a math contest. GETTING SERIOUS. Since then, Leung has parlayed $50,000--from gifts and jobs installing, repairing, and assembling computers--into $450,000. His favorites include Intel, which is up twelvefold, and Microsoft, which has multiplied almost sixteenfold since he acquired it, to $112,000. (An additional purchase is valued at the same amount.) Other picks include Coca-Cola and technology companies Tellabs and Computer Associates. At one point, Leung was worth $550,000, but his fortunes eased as Microsoft's antitrust headaches deepened. As Leung was amassing his sizable nest egg, he watched other students spend their cash on cars, clothes, and music. That worried him, since, after all, his generation ''really can't rely on Social Security.'' To help teens get serious about investing, Leung designed three Web sites (http://library.thinkquest.org/3096, http://library.thinkquest.org/10326, and http://www.stocksquest.com/). So, what advice does Leung offer teen investors? First, take advantage of the fact that mom and dad are paying the rent, and save money. Then, get a parent to set up a custodial account and ''buy a few shares in solid companies that are industry leaders.'' Leung likes Intel, Lucent, and Coke. He recommends index funds for those who are uncomfortable picking their own stocks. Leung likes the Motley Fool Web site for its explanations of investment concepts. But when researching stocks, he looks up Value Line at the library. When Leung has a prospect, he often waits for the market to dip to buy. That way, he can get a stock when its price-earnings ratio is close to its earnings-growth rate. Leung looks for earnings growth of at least 15%. Because it's almost impossible to predict which way the market will go, Leung thinks day trading is akin to gambling. Instead, he believes it's safer and more profitable to hold on for years. And the one undeniable edge Leung and his investing peers share is that time is on their side. BY ANNE TERGESEN