It will be highly dependent on the LTVs, but 2nd's on investment properties get sketchy. 

While it seems like there are some better priced deals lately, you may have to be prepared to put down 30-40% down.I'd say due to the lack of homes for sale, you should be open to many if not most cities depending on the deal that comes up. 

Quote from @Joshua Tucker: What specific tax benefits can high net worth individuals receive from building real estate on tribal land?

Success still depends on your effort, discipline, and ability to execute.

There are likely larger users out than than what I deal with, but at that SF at least in my world you are likely looking at multiple tenants, not sure if thats what you planned or not.additionally something else to consider is the cost of buildout on a med office space. depending if they are going to have x ray or not its not uncommon to see $500-$800K buildouts in my experience. 

Structural engineer is definitely first step as Mason mentioned.It totally depends on liquidity, risk tolerance and time.

It’s not a bad idea just depends how much effort and $ you want to put in.

Depends on if you are hiring a builder to build or if you are the builder yourself. 

@Mike Levene cost to build per square foot is $200-$300 depending on finishes.So, you can start with that.

From what I understand it’s neighborhood dependent up there.