I like the “you can add a window unit” solution provided the AC is working to its best ability.

Simple solution: Inform them that unfortunately you can’t accept ESA letters without being able to verify the validity of the letter by speaking with the local licensed mental health professional who prescribed them their ESA, so that you can verify that they have a legitimate disability requiring an ESA as well as that whoever prescribed it to them is a real licensed mental health professional who has an ongoing relationship with them beyond just receiving a one-time payment to “prescribe” the ESA. 

The problem to the solutions of having a window AC or portable on standby is that if your portfolio is large you will have to have $10s of thousands of dollars of ACs for "just in case" moments.

I personally prefer to be more on the advising and relationship side so I can give my clients more tailored solutions, help them avoid pitfalls, connect them to people that can help them grow and structure their portfolios and I treat this industry more as a relationship business rather than a transactional business. 

There are a few issues and solutions that I can think of, and some were already mentioned by the other investors:1.

I was an agent when buyer broker agency was introduced in VA, as a solution to avoid the many lawsuits post-sale arising from buyer confusion that the agent assisting them actually represented them, when at that time all agents worked for the seller.

A good broker can communicate between multiple lenders and often times has established relationships within the C-suite levels of multiple lenders that they can make calls on your behalf to "shake some trees" and get things processed not just in a timely manner, but in a manner that is on time based on what you are trying to do.Unfortunately it is not uncommon per se, but knowing where these hang-ups tend to happen and how to time everything based on lenders timelines and processes is where it can be helpful to have 'go to' lenders that you are familiar with, and they are familiar with you to help get things done.Good luck though, happy to help where/if I can.

Surprised Pigeon Forge and Gatlinburg is not on this list.Places like Joshua Tree are popular but also very saturated. 

----I do have a 'rental' in Joshua Tree House....

When I worked with them, they were extremely reasonable with their borrowers when credit was not available to figure out working solutions, which steamed from the due diligence and experience they did on the borrowers.Corey Dutton, DFA does not prevent HML on primary residence, it does put rules around loans as they relate to primary residence.