There are several approaches to giving your character a career. One is to give them a job that entitles them to be naturally nosy, such as a newspaper reporter.
Another is to give them a distinctive area of expertise. The plus side is that with each book, you can explore some new facet of their industry. The downside is that if you are writing mysteries, readers will need to suspend disbelief about, say, the growing pile of corpses in the floral industry. Sarah Strohmeyer has done very well with her Bubbles Yablonsky series, in which a hairdresser solves crimes and dispenses beauty tips. John Billheimer’s more serious Owen Allison series stars a “failure analyst” who analyzes why dams fail or plans crash.
A third approach is to give your character an ever-changing occupation. Editors are always asking themselves: What makes this book different from the hundreds of others crossing my desk? Elaine told me, "My hook for the Dead-End Job series was that my character and I both work the same minimum wage jobs. We've worked at a dress shop, a bookstore and as a telemarketer. More rotten jobs are planned." She has a six-book contract.
Another approach is to simply give your character enough money that he or she doesn’t have to work. In the first of my Claire Montrose series, Claire inherits what proves to be a long-lost Vermeer.