The goal is to have that done in the next 2-3 months and then start on rebuilding but not just a home on the now vacant lot, but a duplex.

rebuild only. 

., it's can you rebuild that house + buy that land at less than the market prevailing rate.

I have since decided to rebuild my 3 bedroom pool cabin.  

Okay, I'll jump in here.I've done SBA 7(a) loans, one for 1.7mil and another for 2 mil, for two separate commercial properties (gas station c-stores, ground up raze and rebuilds). 

I believe alot of owners in the area are under insured especially when it comes to loss of income and rebuild costs. 

Here is text taken from the HOUSABLE website for Oakland:Utility ConnectionsCategory One: No new or separate utility connection shall be required.Category Two: A new or separate utility connection may be required, but the connection fee or capacity charge shall be proportionate to the burden of ADU on the water or sewer system.Here are definitions of the ADU categories from the City of Oakland website:CATEGORY ONE ADU: Involves either conversion of space within an existing Single-Family Dwelling, or conversion or rebuild of an existing accessory structure; includes no expansion of the existing building envelope other than up to 150 sq. ft. for purposes of accommodating ADU access and egress only.CATEGORY TWO ADU: Involves construction of a new detached or attached structure, including an exterior addition to an existing structure to accommodate the ADU, in conjunction with a proposed or existing Single-Family dwelling.It seems that Oakland is making things confusing with the language they are using, but I still believe that my original interpretation is correct based on the State Assembly Bill. 

It has been a super fun ride (sans the Great Recession) and I do hope to continue it to rebuild the net worth lost then and continue in the field that I love being in.I know that this is pretty long winded, but it is hard to fit 52 years of investing into one page.

Yeah well, we are getting stronger and stronger hurricanes coming through and if I don't sell prior to house getting destroyed, would only get rebuilding costs from insurance.  

Just my 2 centsTo answer the question if it’s a tear down you need to understand the comps In That area and the cost to remove the existing and rebuild - where many go wrong with rebuilds is they assume best case construction and holding times and time is money especially if using a construction loan.