Meanwhile, I created one LLC and business bank account to pay property tax, mortgage and day-to-day operating cost.

Which is somewhat frustrating if a flipper would pay 5-10k for it at that price.

One of our residents was robbed outside of this property and we ended up paying for the resident to move out and sold this property.

Attend in person, bid, if you win you have to pay right then via a cashiers check.

You can't actually pay it off directly because they've been securitized, and the people who invested in those securities did so because of the specific certainty of the payment schedule.What you do in a defeasance is use the proceeds of the sale or the funds from your new lender to purchase treasury bonds that are packaged to make the exact payment amounts and timings on the remaining term of the loan, and then assign those bonds to your old lender.

How do you pay for the tax and insurance?

Furthermore if they are always paying they probably will stiff you in the end if they know they aren't going to get the deposit back. 

For example, I mention that every adult must pay a $XX application fee, pass my credit/criminal background, make a combined income of 3x the rent, and whether or not the property accepts pets.

How much is this individual paying to park a trailer there?

The unit is part of a condo association for which we pay fees.