And in my case, it was just the Buyer who was asking for it (not a lender). 

I have investors & buyers in the area.

My property failed perk test, making it useless.  

Duplexes are worth quite a bit more per sqft than Fourplexes as there is a larger buyer pool and it opens to the non-investor customer.

Would my tax lien be extinguished if the homeowner fail to pay?

Once you do, you will find eager buyers, and that is "all" it takes.Of course, I simplified it (a little), but that is basically the gist of it.

If I fail to spend all my money before I die, she will inherit the high credit, corporate backed NNN properties I developed/repurposed over the last 15 years.

Assuming you have a one year contract with your realtor:Apart from the usual buyer representation commission, do you have any exclusive clause with your realtor?

As for the extra dollars unaccounted for, it could be a number of things - repair persons fee, management fee, failed repair, etc.

If you fail at that then concealed is a far better option than open carry in my opinion due to maintaining the element of surprise and avoiding all the complications of how the majority of the public views open carry.