What does Barney Rubble do for a living, and how did he land Betty with seemingly no tangible income?

Barney's job (or even if he had one) was never given during the original series. Spinoffs suggest Barney went to work at the Slate Rock and Gravel Company quarry alongside Fred at some point after the original series; possibly in some office role. An episode of the original series does have a brief scene of Barney working at the Granite Building. When speaking to an upper-crust snob in another episode, Betty declares Barney is in "top-secret" work; but that might have been a cover for a low-level job or unemployment, or perhaps an in-joke meaning that Barney's job was unknown even to the show's writers. In one episode, Barney's boss tells him to "put down his broom," which implies some sort of janitorial works is involved. In a majority of spin-offs and movies, Barney has been portrayed as working in the quarry as a dino-crane operator, alongside Fred.