Nobody is living in the unit, the city came out to inspect the unit, nobody was there to let them in (it failed because of this).

I am purchasing a 3acre lot an hour outside Dallas which not only fails to convey mineral rights, but also gives "appurtenant rights to use the surface of the land" to someone back in 1925. 

There is an alternative that involves doing cost segregation on property you purchase and using this to help offset cap gains resulting from failed 1031 Exchange.

My property failed perk test, making it useless.  

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

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.

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

Overall, it can be a profitable business, but most people get into it to become an investor and 99 percent fail right away because they don't know the slightest thing about repair costs, talking to sellers, and are only in it for the money and not to help people.

If he failed to pay, it could be construed to be a failure of consideration so the deed fails and she's still in title with him and all he can convey is his half. 

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.