Also, I found 2 ideologies regarding such development projects: Use one GC for the entire development or use that GC only for crucial trades such as foundation, framing, roofing , external siding, etc. and use sub contractors for finish and interior work to reduce cost.

With only requiring 5% down the money needed is very low compared to the Cash On Cash return you could make on a small Multi Family. 

I don't know any builders here, so I am wondering a few things: - Does anyone have a builder that would be interested in doing a single infill project (there is another infill lot going up on the street, might try and connect with them) - I am in between paying for it myself with cash during construction (maybe the home will cost 150-200k to build?)

Whether to build on your lots now or wait depends on a few things: construction costs, rental demand, and your financing options.

We have converted oil boilers  to gas boilers to reduce costs. 

Over time, cost of insurance, monthly charges, and surrender fees (which can last 10+ years) reduce how quickly your cash value grows.3.Policy Loan Costs & PerformanceYou’ll still pay interest when borrowing against your policy.

Ebooks, podcasts like @Bonnie Low suggested and start running numbers on every deal you see until you know how it all works.

The catch was that it would cost me $7k.

The surprises are often avoidable if not for bad underwriting......specifically underestimate renovation costs or operational costs.....overstate rents or "as complete" valuation.

My father is a contractor so we will be able to complete most of the work ourselves while keeping costs low and add equity.