$518,400 – that’s how much you need to earn annually to afford a median-priced home in San Mateo County. In neighboring Santa Clara County, you need $468,000. Higher borrowing costs and a shortage of available homes for sale have brought California housing affordability to the lowest level in 16 years, with San Mateo and Santa Clara counties requiring the highest minimum incomes in the state for a median-priced home, according to a recent Traditional Housing Affordability Index report from the California Association of Realtors.