I was told by the property manager we can write a letter to the Association that will be given to counsel.  

Here is a good post by someone bombarded with "will you sell" emails, calls, texts and letters. 

You're working really hard to rationalize your profit.Again, the way to move forward is to run this by your broker - and maybe even by your local Realtor's board's legal counsel to be safe (assuming they'll answer that sort of thing - they may not)  If I were your broker (and I'm not), I'd want a very plainly worded letter, drafted by your attorney, signed and notarized by the Personal Representative of the estate and all of the heirs that the fair market value of the property is $100,000 and they are willing to accept $60,000 as a means of selling it quickly, and that they explicitly reject your recommendation of listing it on MLS for $80,000. 

Would you get a preapproval letter from your lender for a 16+ unit?

Whether that's in an ad description, direct mail letter, etc.

Write a strong-worded letter sent via email or mail and remind her that has violated the lease as it is and you can pursue eviction.

Then I took some action by driving for dollars I sent out hand written letters and took phone calls (some very angry) after 7 letters to each homeowner (over a few months) I sent an actual contract offer to every person (interested or not).

We're long-term, buy-and-hold driven, so ideally we want a mix of both appreciation and cash-flow. 

It almost never gets better with a tenant in your situation.On the 6th they get a rent demand letter (soonest I can per statute). 

The plan could purchase a rental property if you thought a rental would provide a better mix of risk and reward than your current investments, but that rental would have to be a purchase entirely removed from you or close family held properties.