That's an off market deal direct from seller. 

Also, what are some good ways to learn how to buy an off market property and/or buy subto? 

Also a realtor that is open to subject to or seller financing.I have recently paid off my first property in Portland Oregon.

As the New York Post article notes, “Under the law, it is illegal for the homeowner to change the locks, turn off the utilities, or remove the belongings of the ‘tenants’ from the property.”

They make a stamp you can buy off of Amazon (or any office supply store) so you don't even have to write it a million times.If you want to be "nice" you could let them know of your plan.

I started with an off-market BRRRR, and then I did another one, and another, and so on.

In that case you should be open to exploring more hands off REI strategies like funds, REITs, etc. 

If Wholesaling is so difficult in So Cal, would someone who lives in So Cal be better off looking at other areas outside of So Cal?

If you can wait 5-10 years to get wealthy off RE then I’d go that route.

I speak from experience.....some might have $100,000 worth of junk you need to haul off....on a  $10,000 piece of property you bought for $1000.