I've seen estimates of $200 to $400 per square foot for SoCal with $700 sq ft for something higher end and building up a hill and but possibly higher for San Francisco Bay Area (lhigher labor costs, etc.).  

In my market, which is a fairly economical place to build, I am friends with full time builders that are in their properties about $150k/door for construction level finishes.  

The seller has the two lots legally separated, but due to deed restriction imposed by the subdivision development, found that building a house on the “tennis court” lot was not allowable. 

Build a local team for cleaning and repairs to streamline operations.

They are literally building their own comps.

Go to BUILD YOUR TEAM at the top of the screen and look for local investors or meetups in your area.

Laundromats that are next to (same building) or attachedwith an access door to a coffee shop, cafe, etc are the best ones to get.

Eventually you'll start developing relationships with people in the market that will bring you off market deals, but they have to believe that you can close the deal.

HighLevel - plenty of build outs for LOs or brokers.

Building small units in small counts is expensive development.