I decided to keep 50 acres to the side for investment purposes and develop roughly 125 acres.

We all need to be relatively certain that 1 Bitcoin will be worth roughly the same amount tomorrow, next week, next month, and next year otherwise it won't become a currency. 

For a lot of things you can just look up material costs and assume the same for labor. 50% material and 50% labor holds roughly true for the entire project, at least for me here in Milwaukee, your labor cost will probably be higher in the Bay Area.100-125k spread would be tight, even for me here in Milwaukee.

Having a PM that knows what to do will help but it might be a rough road ahead of you.

I plan to use a HELOC for the improvements to create lots with improvements.My plan for the rest of the parcel, now roughly 7 acres, is to built a primary home for my family, and to put in 5-6 cabins.

There are multi-million dollar houses that you can walk just a couple short blocks and watch the neighborhood get pretty rough and potentially dangerous.

Now for my out-of-pocket expenses:Down payment: $7500 (Hard money loan 90% purchase price 100% rehab)Closing costs: $6500Inspection: $400Agent's commission: $5200 (didn't raise purchase price of house with seller concessions, so that money didn't apply to the commission sadly. won't make this mistake again)Holding costs: $1300 (one interest-only payment of $770, roughly $200 in utilities and $360 in insurance)Total: roughly 21 grand. 

So on a 12 unit, I would keep an operating cushion of roughly 24-30k. 

Roughly 8.875% on a 30yr Fixed fully amortized. 

550k roughly-Or new duplexes with 4 bedroom units and a garage?