Answer by taking a quote from the following article:

Gavin Christopher Newsom was born in San Francisco, California, to Tessa Thomas (nee Menzies) and William Alfred Newsom III, a retired state appeals court justice and attorney for Getty Oil. He is a fourth-generation San Franciscan. His father is of mostly Irish descent; one of Newsom's maternal great-grandfathers, Scotsman Thomas Addis, was a pioneer scientist in the field of nephrology and a professor of medicine at Stanford University. Newsom is the second cousin, twice removed, of musician Joanna Newsom.

On May 14, 1991, Newsom and his investors created the company PlumpJack Associates L.P. In 1992, the group started the PlumpJack Winery with the financial help of his family friend Gordon Getty. PlumpJack was the name of an opera written by Getty, who invested in 10 of Newsom's 11 businesses. Getty told the San Francisco Chronicle that he treated Newsom like a son and invested in his first business venture because of that relationship. According to Getty, later business investments were because of "the success of the first."  One of Newsom's early interactions with government occurred when Newsom resisted the San Francisco Health Department requirement to install a sink at his PlumpJack wine store. The Health Department argued that wine was a food. The department required the store to install a $27,000 sink in the carpeted wine shop on the grounds that the shop needed the sink for a mop. When Newsom was later appointed supervisor, he told the San Francisco Examiner: "That's the kind of bureaucratic malaise I'm going to be working through."  The business grew to an enterprise with more than 700 employees. The PlumpJack Cafe Partners L.P. opened the PlumpJack Cafe, also on Fillmore Street, in 1993. Between 1993 and 2000, Newsom and his investors opened several other businesses that included the PlumpJack Squaw Valley Inn with a PlumpJack Cafe (1994), the Napa Valley winery (1995), the Balboa Cafe Bar and Grill (1995), the PlumpJack Development Fund L.P. (1996), the MatrixFillmore Bar (1998), PlumpJack Wines shop Noe Valley branch (1999), PlumpJackSport retail clothing (2000), and a second Balboa Cafe at Squaw Valley (2000). Newsom's investments included five restaurants and two retail clothing stores. Newsom's annual income was greater than $429,000 from 1996 to 2001. In 2002, his business holdings were valued at more than $6.9 million. Newsom gave a monthly $50 gift certificate to PlumpJack employees whose business ideas failed, because in his view, "There can be no success without failure."  Newsom sold his share of his San Francisco businesses when he became mayor in 2004. He maintained his ownership in the PlumpJack companies outside San Francisco that included the PlumpJack Winery in Oakville, California, new PlumpJack-owned Cade Winery in Angwin, California, and the PlumpJack Squaw Valley Inn. He is currently the president in absentia of Airelle Wines Inc., which is connected to the PlumpJack Winery in Napa County. Newsom earned between $141,000 and $251,000 in 2007 from his business interests. In February 2006, he paid $2,350,000 for his residence in the Russian Hill neighborhood, which he put on the market in April 2009, for $2,995,000.

Where did he work after that?
he became mayor in 2004.