There are multi family listing available in the area. Please look for investment properties in San Mateo County and these listings come and go. If you need help from agents/Broker they will be able to send you that information.
That's a great idea Roshan. There are duplexes and multi residential properties available, but they do go fast, especially right now with rates so low.
Find an agent you can trust. The best way is for a friend or relative to refer you to someone or maybe someone online. Ask for referrals from past clients. You cannot afford to make a mistake in real estate, it's much too costly.
There are several multiu familoy properties for sale. What specific area are you looking ? Are you lkooking for duples, triplex or 4 plex. When you go over 4 units it is then considered an Apartment building.