SAN FRANCISCO — In June 2007, Evan Williams was looking for investors for a quirky Internet communications service called Twitter that he had co-founded.
Dick Costolo, chief executive of Twitter, was an early investor. He will most likely earn millions from the initial public offering.
He had already signed up a number of well-known Silicon Valley financiers, but he also dashed off a note to his old friend Dick Costolo, who had just sold his company to Google, asking if he would like to put in $25,000 or $100,000.
“I’m on the $25k bus,” Mr. Costolo replied three minutes after receiving the e-mail. “Thanks Ev, this will be a lot of fun.”
Mr. Costolo, who is now the chief executive of Twitter, is one of a handful of individual investors who stand to reap the rewards of a potential initial public offering of stock in the social network. The company said on Thursday that it had filed early paperwork with regulators to conduct such a sale, which will probably occur late this year or early next year.
Although many details are still unclear — most of all the offering price of Twitter’s stock — Mr. Costolo’s initial investment is probably worth more than $10 million, with additional shares he has received as an executive worth many millions more, according to people knowledgeable about the company’s finances.