Also, with these homes you can get away with window air units. 

Looking in the area or the University of Arizona and Davis Monthan Air Force base.

The main question is: what are the important questions to ask, what documentation should a private lender ask for, and what guidelines might be suggested to prevent problems from arising from a private loan?

They start off with basic property configuration (bedrooms, bathrooms, etc), then consider costs (heat, provided appliances, etc) and features (central air, ceiling fans, etc). 

This is flat out incorrect in many casesHere is my 5%- 3/1 with central heat/air, fireplace and carport outside of Lubbock. 

If you don't have some sort of air circulating, it can cause condensation.

Shiller was making the comparison by saying that shorting the stock market helps prevent bubbles from forming and that the use of CDO's in 2003-2006 was an attempt to mirror that action for the housing market in order to hold down the bubble, but it was a fail. 

Can I prevent them from moving in at this point unless a payment is presented?

Especially, if it prevents property to function as intended (restricted access to mailbox, unable to use part of the driveway) it's more of a repair than the maintenance?

and that in turn is the whole reason why mortgages (deeds of trust) employ due-on-transfer acceleration clauses to prevent the collateral (property) the mortgage loan was secured against.