How to afford a house in SoCal/ Greater Los Angeles area?

How to afford a house in SoCal/ Greater Los Angeles area? - 1
Added (1). I know very little about how it works on buying a house and I recently started seriously considering buying a house. I am 25 years old, single. I have a credit score close to 780. I have no debt. I live in Southern California, greater los angeles area. I have a very stable job and I make $70K/ year before taxes with 3-5% salary increase a year. I live at my parent's house so my current living expenses is $300/month, which is pretty much how I've been saving my money.
Added (2). I have close to $100K cash, with roughly about $20K in stocks/ bonds. Many houses I see in my area seem to hover between $400K to $600K… I've read that 20% down is the golden rule, but I've read that mortgages are based on your income, typically up to 3 times your income. How can I afford a $500K house, given my situation?
Added (3). My income is small compared to the average home price in the area… $100K down payment + 3*70K = $310K.

Does that mean, given the situation I have right now, I can only afford a $310K house?

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