The precipitating factor was this couples adamant desire to purchase the property which allowed me to negotiate a price that, after discussing with my realtor, I feel meets or exceeds what I would get if I listed. 

I desire to approach Buy and Hold via Brandon Turner's term "house hacking."

I found out to not use national banks as their deals don't particularly favor my desires.

HelloI recommend to start out without using no money ...zero dollars..If you have the drive and desire to make this happen you can do it...Below is a link to a ton of free information...http://www.flip2freedom.com/

If/when somebody buys the community I'm thinking this lot may become desirable to a builder?  

Depends on your desired annual return and how active or passive you want to be.Also if you have 10,000 to start or 1,000,000 etc. 

Some markets are more desirable (say where you can rent a home for 700 and the lot rent portion is 300, and you have a good spread).  

A 15 grm is not a very desirable number Smaller is better in grm terms

Other than the 90 hour learning and exam and licensing, where should one start with little to no knowledge but desire to get into the business?

Make sure of your desired market's information every time.Best to you!