Another payday awaits private equity investors that took the HCA hospital chain private four years ago, including members of the Frist family of Nashville. The family is expected to make at least $15 million from selling some of their shares in the initial public offering that would mark HCA's return to being a publicly traded company. That's based on the midpoint of a targeted stock price range of $27 to $30 per share revealed in a financial filing on Tuesday. HCA itself expects to net $2.4 billion after the stock offering, and will use the money to pay down debt, among other corporate purposes. The Frist family, other HCA executives and private equity firms Kohlberg Kravis Roberts & Co., Bain Capital, and a unit of Bank of America's Merrill Lynch subsidiary are expected to sell 36.3 million shares and net about $1 billion.