Private equity companies are most like

commercial banks that lend money to private companies but convert debt into equity when the companies are unable to pay back their loans

investment banks that acquire small stakes in private companies and sell out for a profit when they grow and go public through an IPO

credit unions that restrict membership to fellow employees in the same organization

mutual funds that pool money from common, low$-$income investors to acquire minority stakes in public companies to benefit from dividend income and capital gain

hedge funds that pool money from sophisticated, wealthy investors to completely buy out public companies and take them private