I moved out almost immediately after high school completed, and into San Francisco with my (much older) girlfriend. So I guess I was 18 when I moved out. That's where I lost almost all of my school friends (who went off to college, while I went to work in the Silicon Valley tech industry), and got involved with a completely different social group. (SRL, Cacophony Society, and other early Burning Man people, as well as the funk-metal scene of Primus, etc.)
Lori and I had an apartment in the Sunset District of SF for 2 years. Then we broke up, I moved into the Haight-Ashbury, and got another girlfriend.