How many properties did it take for you to feel like you had a stable understanding of the concepts involved.

Policy is only about $300 per year but its a basic policy.

Basically any advice that could help steer my path to acquiring 100+ unit complexes.

That's basic sales skill.

I introduced the concept of the seller financing the sale and explained all the benefits to the seller.

Basic philosophy is to structure the investment not only for maximum rewards, but also for minimal risk.

They purchased the property back in late 2013 for $245,000 and have put about $100,000 in renovations, so the property is basically turnkey. 

They have tiny cabins available for sale, or rent to own (basically financing) and they have repo cabins at great prices.

I believe Lending Home does gap financing which basically can bridge the difference between the money you need and what they would lend under normal circumstances e.g. 75% ARV

Check with Planning and Zoning to see what's allowed and what the future plans are for the area.With this basic information talk to local real estate agents and maybe some small builders who do infill houses.