I installed a high SEER Mitsubishi 18,000 BTU heat pump / AC and then had an AC technician come out at the end to vacuum the lines and do the final electrical hookups and verify everything was good all for under $3k.

If it is a 2 bedroom even in Alton Park without central air and heat rents have gone up, and in many cases they are still increasing. 

Made a move into Radioactive Materials Remediation (I know weird move) and was hired by a large oil and gas company 2.5 years later as their Radioactive Materials Manager, learned explosives compliance along the way and spent my last 5 years there traveling all over the U.S. as their Corporate Radiation and Explosives Manager. 2017, Good Job, Good Pay, New Baby and then a heating fuel oil truck had a spill on my property and made its way into my home and under my homes footer, DEP got involved and to remediate it they had to tear down the house and we lost everything.

@Martin Taylor Well disadvantages of thermofoil easy to peel, easily chipped, sensitive to heat.  

I got into a heated debate with a close friend on where we see the real estate agent in the next 10-20 years.

(Not that there is anything wrong with that) (PC).OK- Back on target-  Here is my list-  I will try to add to it as a resource- Maybe put a link together-  1:  Air circulation/Heating-   PTAC, or MiniSplits (Anyone make one with a UV-C virus bypass/intake)?

$500 isn't too bad at all.We had a big one go down & a couple of neighbors who have those outside home heating furnaces offered to cut it up & take all the wood.

The test consists of 4 elements:It is an investment of moneyThere is an expectation of profits from the investmentThe investment of money is in a common enterpriseAny profit comes from the efforts of a promoter or third partyIf you are borrowing money from someone it generally fails the third element above because there is no common enterprise for those contributing the labor and the capital. 

In the future we are also looking to add a second boiler to separate gas heat utilities. 

So this is a bit of a lessons learned / warning when it comes to repairing certain elements in rental properties.