Construction Costs Brentwood/Bel Air

[TJ Karwal]

Hi all! This is my first post here and have learned allot from poking around. I currently own a home, but am very interested in buying land and constructing  a home and for my family and I.  I am looking at several pieces of land in the Brentwood/ Bel Air area in southern CA. Does anyone have experience or any insight into what I could expect to  pay for construction to build from the ground up? Also, Some of these listsings have plans all ready approved and ready to build, and other don’t. Are there any potential pitfalls or gotchas that I should avoid when looking at land? 

Thank you in advance!