In October, the median price for a single-family resale home in San Diego County was $610,000. Mortgage interest rates at the end of October were 4.97 percent, said Mortgage News Daily, meaning the monthly payment for a 30-year, fixed-rate mortgage (assuming 20 percent down) was around $2,610. But, interest rates were up 1 percent from the same time in 2017, increasing the monthly cost by roughly $289 in a year.