@Andrew Postell at least in NC, if the borrower gives constructive de facto notice at time of origination, via a deed accepted by the underwriter and funding is permitted to proceed (there is NC COB precedence), then there is no default and the bank cannot "call" the note. 

If you want to be more pro-active - drive your vehicle to that vacancy -Talk to as many neighbors as you can - let them know that you are interested in that property (or others that they may be able to refer you to) some neighbors won't cooperate with you since they may think you are a bill collector.Get the tax ID of the ownershipGo to white pages - search for the ownersPut a notice on the door for the owner to call youCheck to see if it has housing code violationsLiens - see if you can buy the lien and foreclose (or take an option to buy the lien - forecloses on your option)Check to see if it is in Tax Sale - contract the tax sale purchaser to see if you can take assignment of their positionCheck to see if it is in foreclosureMake sure you look at the back of the houses - talk to the neighbor at the rear of the housesFind out if it has been listed - by whom and for how long - call the real estate agent (they are the ones who know how to contract the owner) ask the agent "are you still accepting offers on that property?"

Request accepted!

I know in Chicago lot of landlords don't accept security deposits anymore.

We've had LOI's accepted without ever seeing anything beforehand.

Assuming the property does not have major issues such as deferred maintenance or lacks desirability, accepting anything less than 20% down, minimum, is asking for problems.  

Will the tenant accept a cash for keys offer, offer them $1k in exchange for possession and no eviction on their record.4.

Accept a wire transfer only.

Both offers were accepted and both properties were UNDER the ARV and the appraised value.

However, it should be expected to discuss services needed/rendered and negotiate an acceptable price between the two parties.