MIAMI — For the Ingram clan, working for the Miami-Dade County transit system has led to regular paychecks, a steady advance up the economic ladder and even romance.

By driving buses in Miami’s sun-scraped communities, Richard Ingram and his wife, Susie, were able to join the ranks of the black middle class, moving with their four sons from a rental in the down-and-out neighborhood of Overtown eventually into their own house in central Miami.

Two of their children later followed them to the county bus depot. The eldest son, also named Richard, met his future wife there when she was assigned to the same route as his father.

“I tell you, my job is a godsend,” Richard Ingram Jr. said.

Now his older son, 21-year-old DQuan, is applying to take the transit system test, hoping to become a third-generation driver. But Mr. Ingram said that unlike when he was hired, today the competition is tougher and the jobs are a lot scarcer.