A Lyft car drives along Powell Street in San Francisco, California. Getty Images

Given the sheer number of first-time driver applicants who don't have qualifying vehicles in the cities where the companies are first launching the program, Zimmer is confident in the program's viability. According to Zimmer, there have been 60,000 first-time applicants in Chicago alone and 150,000 across all four cities. "This is geared toward the millions of Americans across the country [who] don't have access to a vehicle that is qualified to drive for the platform," Zimmer said. "This solves a major component of it that probably isn't possible without the type of relationship we have with General Motors, so it becomes a big differentiator." Uber also began offering a few weekly car rental programs through partnerships with Enterprise and a Cox Automotive company called FlexDrive, though the former costs the driver $210 a week. The company also offers long-term leasing agreements through a program called UberXchange that allows drivers to back out of the contract with two weeks' notice without being penalized. That wasn't always the case, however. Before the summer of 2015, drivers had few flexible options through Uber. Drivers could rent a car from and pay weekly rent to a fleet partner, finance a vehicle through a partnering bank like Santander, or commit to a long-term lease.