So you are a cash buyer looking for good returns with some long term appreciation, and a retirement home? Cap rates in California are generally lower than many other parts of the country due to higher home values. Investors in the past relied on appreciating values, but the prognosis for that does not look good over the short to medium term. Managing rentals is a headache so if you want passive income you need to look for reputable property managers first, and decide on the demographic you feel comfortable with. That will determine your investment type, risk and returns. A simple rule of thumb is you want $1 in rent for every $100 invested. So you should be looking to achieve rental income of $5000 per month on your $500k invested. Then expect to pay away 50% of gross income on expenses. Single family homes in the $100k price range can just about achieve this but you will not find many in San Diego. Even multi units will be a challenge, unless you look in south central LA, Rialto, or places like Modesto. Single tenant triple net commercial RE offers good hassle free returns, but they come with a bigger price tag. Not sure the land suggestions above are serious.
