Squatter/Cash for Keys Questions

[Nicole Clemens]

Quick question:

So I'm preparing my agreement letter for my squatter to sign to vacate the property in exchange for cash and I came up with two scenarios that have me worried:

1-  How do you protect yourself from the squatter giving you a fictitious name?  Let's just say I have an agreement between myself and Jane Doe and after receiving the money, Jane decides to break back into the property and demand more money.  When I pull out my agreement to the police/court/whoever, Jane 'doesnt know what I'm talking about' because 'SHE is not Jane Doe' and she didnt sign that agreement or receive money from me?  

2- What happens if Jane Doe IS in fact living in my property and she DOES take the cash and leave, but what happens if Jane isnt the only one living there and once I give her the cash, change the locks etc some other people show up and waive their piece of mail stating that they had been living there too.  As far as I know, Jane is the only one living there, but that's only because I sent a letter to the occupant(s) asking them to contact me.  What happens if Jane intercepted the letter and kept it for herself because she wanted all the money for herself?