I want to discuss if terms I am speaking of are a possibility.I didn't pull these out of thin air tough..

@Dan LieffortUpgrading to an HVAC/ Central Air isn't a necessity, but renters want them.Window units are extremely inefficient and cost a ton to run the majority of the time.In my multis I get more money per unit 100% of the time.As far as cost goes I would just get a couple of GC's/ AC guys and go with who you trust to do the work, has competitive pricing, etc. and keep your tenets happy.I can refer you to people if you need.

Another scenario is if we experience another great depression, or prolonged recession. 

First thing first, you will have to determine if the price is reasonable to FLIP or try to do an Air bnb model for high cash flow.

I am posting to introduce myself, thank the community for all the value provided and leave a bit of insight into what drives me and what I am trying to learn.So first, I am from Bel Air Maryland.

That basement unit is for air bnb

http://asm-air.com/airconditioning/top-10-air-conditioner-brands/ 

Move on, keep your friends, never rent to family/friends again, and fix the lease agreement for the next one.For the upstairs/downstairs heat differential, that is often easily remedied by turning the central air fan on full time or if it has a circ option, use that.  

I feel as though upon coming back they will frown upon our hiatus, and it will prolong the approval process for a loan.

I will definitely keep what you said in mind when I'm looking since I know that it's better to be paying my rent into equity rather than thin air.