Daly City has project "Home Safe" where under certain circumstances a single family home can get converted to 2 units, with 2 kitchens; there are restrictions of course. One of them is that the owner supposed to live in one of them to rent out the other one. What you mostly see in DC is the fact that people add additional rooms downstairs, sometimes with permits (legal), sometimes without permits (unwarranted) and then add a kitchen which is in most cases not legal or it would show up on the 3R report from the building department which is required on all Real Estate sales within the city limits. The answer to your question will be in the 3R report. As a buyer get the help of a local Realtor. It does not cost you anything more since he is paid by the seller and will give you peace of mind and insurance for the transaction.
Give me a call when you are ready to buy!
Andre Mettler 650 303-2520