For many years, brokers could buy vacation homes in the Hamptons just by executing trades. But when the stock market tanked, individual investors fled, and they\u2019ve been slow to come back. "The old model [for brokers] failed. That is, I\u2019ll tell you what stocks to buy as they go up," says Shaw Lively, research manager at Financial Insights, an analyst company.Today, the buzzword in the financial services game is diversification. Companies are trolling for new revenue streams by trying to become one-stop shops for all their clients\u2019 financial needs, including tax planning, asset allocation, mortgages and insurance. And the most sought-after clients are those who think they need (and can afford) the most services. So Fidelity, Merrill Lynch, UBS and other financial services companies are all in hot pursuit of a bigger slice of the high-net-worth customer pie (Merrill applies the moniker to people with $1 million or more in assets, excluding primary residential real estate). And there are plenty of them: 2 million in the United States at the end of 2002 (a slight drop from 2001), according to the "2003 World Wealth Report," published by Cap Gemini Ernst & Young and Merrill Lynch. These customers provide nearly two-thirds of the more than $1 trillion in assets that Merrill\u2019s Global Private Client Group manages.