San Francisco is an extreme example of a place in California with both a large population (829,072) and high per capita income ($49,986). In fact, it has the highest per capita income of all places in California with a population of over 100,000. Though Sunnyvale ($48,203), San Mateo ($46,782), Thousand Oaks ($46,231), and Carlsbad ($44,305) join San Francisco to make up the top five places in California with the highest per capita income in that population class, none of them have populations even close to San Francisco. The next place with a population similar to that of San Francisco that appears in the per capita income rankings is San Jose ($34,992), and at this point, the difference in per capita income with the entire state of California is only about $5,000.
How to Monetize: Affiliate marketing works well when you discuss products on your blog. For our fish tank blog, we would link to all the things you need to buy for an aquarium and then when people click on that link and buy that item (and other items they purchase with it with some exceptions) you get a percentage of the purchase. Amazon Associates is the best-known affiliate marketing program, but there are others like Impact Radius, ShareASale, Commission Junction, ClickBank and Rakuten too.
If you are expert in some area, you can always give your consultancy service to smaller businesses who cant hire big companies. When we were brainstorming with a client of ours to generate second line of income, he identified that he has some great knowledge in the area of terrace gardening. He could see that he can help families with large enough terrace to setup their own balcony garden and earn some fees over weekends or extra time.