In just two weeks, Tesla will start delivery of the Model 3, its long-awaited $35,000 sedan. After handing over the first 30 sets of keys, Elon Musk will hustle back to the factory, where he hopes to build 20,000 more of the'affordable' electric cars by the end of 2017. Then production really accelerates: Musk has pledged to build 500,000 cars in 2018, more than double the total number of vehicles that Tesla has sold, to date. Even if Tesla can deliver all those cars, cashing checks is but a tiny part of building an automotive business. Perhaps the bigger challenge for the Silicon Valley outfit is building the infrastructure that will keep its cars charged, and fix them when they break.