It has four 2 bedroom 1 bath units and each unit collects $525 per month on rent.

This may be a question for the towing company, but someone might know - does she get charged immediately when the truck is called or pulls up, or must the vehicle be physically towed.Do have to make an addendum to the lease and have her sign in it in order to collect the towing fee?  

I recommend the whole Rich Dad Poor Dad collection, including the affiliated books by Ken McElroy, Carlton sheets, and a few others.

What is the realistic way of collecting unpaid rent, even partially ?

Even if they show proof the day they move in, they could drop it the next day. 

Many sellers require proof of funds and will not accept letters from private lenders9.

@Deryk Kennedy like @Erik Hitzelberger says you must be licensed to manage rental property and collect a fee as compensation (in Kentucky), however that being said...you do not have to be licensed to work for a property manager as a W-2 employee.

Now my RE agent told me that the aunt/ caretaker of the owner (who was living in the house), which is also in foreclosure, has decided she owns the property (without giving any proof) and has now hired a lawyer so apparently now it has to go to probate? 

Jones wants to sell me the property or basically the right to collect the balance of Ms.

The "new" collection company now owns the lien and the lien is still attached to your property.This could be a good news for you now that the loan is with the new company.