I know that developers in the area have rezoned these kinds of plots and built apartment/office buildings and other commercial developments.I want to bring in an investor or developer to the deal who could provide the funds and knows the ins and outs of zoning.

Build a pro team to assist you.

Otherwise, the costs of building pre-fab vs. stick seem to be pretty similar.

Please share reading material , getting started guides or books that might help.I am currently based out of the San Francisco Bay area and I am looking to invest within a 2-3 hour driving range.RegardsYour main goal is to understand the market (demographics, traffic volumes et cetra) and understand what makes a good deal (look at what has actually sold and at what price combined with building out a pro formas to understand it).  

PLUS, good property management companies are great to build relationships with; they see and hear of off-market deals.

I have also aquired vacant lots that I plan on building duplexes on...

I wanted to expand onto other investment strategies to build equity through the BRRRR strategy rather than just buying investment properties off the MLS.

I am a certified building contractor and a certified underground utility contractor.

I think, generally speaking, this is one of the bigger reasons NOT to build an ADU in your backyard simply because you have the space: there aren't really any simple ways to finance the building costs. 

i.e 500k (400k building+100k land cost),  with cost segregation average 400k X 20% = 80kcan 80k deduction be applied as depreciation, against his w2 income from a salaried position?