To be honest I need one rented before I can risk starting the other or else I might be in a financial bind.

It still puts me in a bind with a lot I can't rent and I am sure that soon the village will be complaining about an abandoned mobile home.

Signing a lease with a non owner is not a legal binding contract.

You also have a legally binding lease contract, follow it.

This excerpt is from the South Carolina landlord tenant act:“If the tenant does not sign and deliver a written rental agreement which has been signed and delivered to the tenant by the landlord, acceptance of possession and payment of rent without reservation gives the rental agreement the same effect as if it had been signed and delivered by the tenant”Unless I am mistaken, if this case was in South Carolina, her paying the new rent after you’ve delivered a signed lease would effectively bind her into the new lease, even if she didn’t return the lease signed.

It just means they may not be considered binding in many circumstances.In this case, the written notice states January 12th and that is what I would use for determining move-out date. 

It would be cheaper for you to pay for a fat life insurance policy for them.I don't know your rental market, but if the normal market there is such that you can't get a unit rented for 6 months to a year, it's time to sell it and at a loss if necessary.

This is legally binding in CA at least.  

It has put us in a bit of a bind.

He is just now claiming a misunderstanding / misinterpretation of the deal.well if its in writing and legal binding contract then i dont think there is much to worry about..