Growing startups that wait a long time to go public sometimes face the problem of shareholder equity. Fortunately, there are new ways to handle it. It goes like this: Employees who have vested stock options at thriving startups feel like they can’t leave. They either can’t afford to exercise the options or deal with the ensuing tax bill. Companies also don’t want to let employees freely sell the stock, believing it could confuse their equity capitalization tables.