Elon Musk just spent $1 billion on Tesla shares. He'll have to spend a lot more to ramp up his control.

Source: Business Insider

Elon Musk, CEO of Tesla Motors, waves during a news conference to mark the company's delivery of the first batch of electric cars to Chinese customers in Beijing April 22, 2014. REUTERS/StringerElon Musk plowed $1 billion into Tesla shares on Friday, a filing revealed on Monday. The Tesla CEO raised his stake to 12.