If subject to, purchase price, date of possession, date first payment, date of walk through, etc.

I NEVER let keys out of my possession.

Yes, that's part of our "taking possession" checklist when we close on a new property with existing holding tanks.Because energy efficiency is part of our {self-imposed} mandate we frequently experiment with new ideas during major retrofits (hence the solar thermal DHW with in-line heaters for the final lift).  

She has the keys so she has possession even though she never moved in.What should I do?

In order to pursue adverse possession in California, one must have pay the tax note for the property for at least 5 years, and have open and notorious possesion of the property.

I would suggest getting the contract put together with her understanding she cannot take possession until OCT 6th (or whenever day 91 is) 

What must the agent possess that will make you commit to that person for a long term business relationship.

If, when neither the legal title nor possession of the subject matter of the contract has been transferred, all or a material part of the subject matter is destroyed without fault of the purchaser or is taken by eminent domain, the vendor cannot enforce the contract and the purchaser is entitled to recover any portion of the price that the purchaser has paid. 2.  

Square up and get him to sign some sort of property possession termination where it is outlined the deposit return numbers are final.

If you get them served personally at the residence (where you know they'll be , you'll be able to sue for monetary damages as well as possession of the property.