Really just trying to figure out all the due diligence I need to execute on each property before a purchase. 

Know who the big players are and if they are vulnerable to a change or even if it can be affected by changes in Climate.Getting a lot of these kinds of knowledge only make Common Sense.... but as the saying goes, if Common Sense was so common, would we be saying it that way?! 

So people could have bought properties in Plano and Frisco, and then sold or rented to Toyota executives.

The more I've thought about it, I'd really like to plan out the use of the full 10 acres from day one, even if executed in phases.

If I'm reading you right, you have a fully executed contract in which the seller agrees to pay for certain expenses / repairs, and is now refusing to pay for them.I'm also presuming that the $20K reduction was within the contractually allowed due diligence period and was agreed to by the seller within that same period.If that's correct, the seller is in breach of contract.Your attorney should contact the seller and give them the option of performing to the contract or being sued for "specific performance".  

Do you think the current executive branch is held to any executive action from the Obama administration?

And, to boot, one day after closing they found me a tenant and executed a two-year lease at the exact rate that was quoted in the estimates.

Once I figure out most of question 5, I will know if I am able to possibly execute the buy and hold until the units come online.  

The rents can only be counted once you have a lease agreement executed and in some cases deposits in hand.

FHA will not do a loan where the seller has been on title for 90 days or less from the time the seller gets put on title and the execution date of the purchase & sale agreement.