A majority of the leads I get feel scammy.

I think you'll find leads that way. 

Or they are just collecting leads like spam email marketing then sell the potential leads to wholesale buyers?

I said "Potential Lead".

You also have to spend money on marketing and getting those leads...and with real estate in general, you have to know your numbers.

Consider working to with a list broker to find off-market leads that aren't being targeted by all the other investors in your area.

If you want to acquire more real estate, find tired landlords and get them to do an owner carry while you take over the property and manage it for better returns for you and less headache for them.No matter what route you go, you will need lead generation.

Transaction costs will eat into potential profit, or even lead to a loss.As for future values in SF, of course the city is going to bounce back in 2-3 years big time.

Listsource is a great place to start gathering leads to market to.

This leads to all sorts of market distortions and inefficiencies.Last I heard California is still a democracy so "the politicians" were elected by the people of the state, and are doing what the people want them to do: to perpetuate the endless growth myth of the post-WWII boom, during which California grew on cheap oil, cheap labor, and cheap federal money.