Airbnb Inc. hired Blackstone Group LP’s Laurence Tosi as chief financial officer of the home-sharing startup in July 2015. Tosi had been CFO of Blackstone since 2008. Since then, the world’s biggest manager of investment alternatives to stocks and bonds has doubled assets under management to $333 billion from $119 billion. Tosi has long been drawn to technology. When he was at Merrill Lynch & Co., he helped create Ipreo Holdings LLC, the financial data provider that Blackstone and Goldman Sachs Group Inc. bought last year for $975 million. At Blackstone, he helped start iLevel, a tool for gathering data from an investment portfolio and packaging it for reporting to clients, including on mobile phones and tablets.