I’m considering having a lawyer send them a certified letter, though I know that will still come with a significant fee, which is still preferable to full service.

Do you have someone that manages it all including bookings and customer service or just specific parts like cleaning only? 

Now use 50% expense rule implies $2k expenses not including mortgage service.  

For example, if the area is rural you might wish to have the house inspected, the well tested, and the septic system inspected by separate services.

So I guess the question is how long will it take for the general public to realize that 7% is the "new norm"?

The list is a combination of private and public data. 

We don't allow any "deal-making" in the forums, which includes advertising your services or properties, looking for partners, etc.

You could go either route but don't mix the two in concept as one is a mule and the other is a horse.And, the requirement that properties be listed for sale by a bank is a bank regulatory issue having nothing to do with the NAR, it ensures that the property is held for sale in a public market at its assumed fair market value.

So how do I socialize the benefit of doing something like taking a 200k ADU construction loan to add $X in top line and $Y after servicing the new note, but with an increased property value etc etc? 

If you don't have experience, hire a public adjuster.