Wouldn't the prior leases no longer be valid once the property has changed hands, regardless of how long until their former renewal date or the stated duration of the old lease? 

Investment in a Qualified Opportunity Zone Fund is the closest comparable.  

However if it takes a week before I can get into it and a 3 weeks before I get the leads, how can I really know if I have something that will work prior to that 30 days being over?

This number must be lower than #7 or walk away.9 - Use above numbers to project what the maximum Purchase Price can be for a Rental and/or a Flip10 - Compare them to the actual numbers in the market you are analyzing. 

There are other comparable homes that are nearby, but they are not zoned multi-family.

So compare the $50 for three months, to $600/quarter in the city.

I am prior Army so I understand the BAH and the military life, that is one reason I am looking to invest around military bases. 

If i am sure that I will go the Rent strategy, I would spend a bit more to put in more durable finishes such as tile flooring potentially higher grade countertops and casework, etc, compared to flipping.

Find some comparable properties to index your rental against.

Certainly would want to have the exit strategy figured out prior to purchasing.