You are looking at financial cautious owners with large equity and not selling. While demand for Monterey Park is high, supply hasn't been sufficient. If you drive to (or search) other neighborhoods you'll see more for sale signs. So with a lower median income, budgeting skill, and large equity one can afford housing. They could as well purchased these homes many years back. Don't forget another factor, wealthier landlords may not be living in the same zip code you are counting.