Family Business Deals Fuel Carvana’s Explosive Growth

When Ernie Garcia III came up with a plan to disrupt the used-car market by taking it online, he got help from his auto-dealer father.

A decade later, the company he created, Carvana Co. , is worth nearly $40 billion and sold around 400,000 cars this year. It is still leaning on Mr. Garcia III’s father for support.