By the same token, I don't believe your repairs and maintenance expenses would decrease because you are charging a lower amount of rent per month. 

I managed the rentals myself up until early this year when I hired a property management firm in order to get some free time back, have some backup so I can go on vacations again,  and in response to the hostile political environment towards landlords in seattle.My long term plan with REI is to get to a large enough door count such that with sufficient equity the net cash flow is enough to live on comfortably  (which I would define as matching my current gross software engineer's salary).    

There are other loan options out there besides FHA just as a heads up (5% and 10% down without having to pay the high "costs" associated with FHA loans).Each person has their own take, but if you are going in as an owner occupant I would personally advise trying to find not only a 2-4 unit, but a 2-4 unit with at least one current vacant unit so that everything can be a little bit more straightforward on the purchase.Also, if you do go the FHA route, the 2 unit one might be your sweet spot. 3-4 units have a self sufficiency test that doesn't usually pencil that easily in the Bay Area.

What about contractor investors who already have General liability coverage from their contracting business, would a vacant coverage be sufficient enough?

I understand that most banks like to use this formula: (Value of home - amount owed) .8I have enough equity in the home to where 80% of the difference in value minus balance is sufficient to fund my construction project. 

That will only be a concern if you are making token earnest money payments and they are bankrolling the construction. 

If your primary still has sufficient equity, why not take an additional loan on it? 

I visited sites similar to this, but didn't find information to be sufficient enough.  

The climate is rapidly changing, full time agents are becoming more and more self sufficient, however, very relying on technology.  

And if you have sufficient cash flow, reserves etc. by definition you aren't over-leveraged for most circumstances.