Although a written agreement is not necessary where the collateral is in the possession of the secured party as a pledge, a security interest is usually not enforceable unless there is a written security agreement, signed by the debtor, describing the collateral.

Ask for immediate possession before settlement.  

From what I've been told, they are great people and great tenants, but if I take possession of the house, I'd like to increase the rents to be somewhat closer to market rate.

Or is it best that you not possess a graph for that?  

(Contract for Deed) The home closed in September of 2010 and the interpreter took over his property in December of 2010 and has had possession of his property ever since until a court recently awarded possession to his wife who received the property by way of a Quit Claim Deed. 

@Wayne Brooks, @Jason Reinstead  Be sure to both write and phone that you are canceling AND that you know they do not possess a current license which is being posted to the State Contractors Board.  

Since they were still there we will continue with the Warrant of Possession. 

The property is being sold subject to: All taxes due the municipality not foreclosed by this action,Water and sewer use charges not foreclosed by this action,All building and zoning regulations of the municipality which affect this property,All building lines, easements, restrictions and all other matters concerning this property which appear of record,The rights of any person in possession or occupancy of the property who have not been made parties to this foreclosure action,The right of the United States of America to redeem the property, if applicable under Federal law,Any other liens on this property which have not been foreclosed by this action."

What are my options for taking adverse possession?

If you simply hold onto the property for ten years after the tax deed date, and maintain possession (usually by renting it out) then you are into old fashioned "color of title adverse possession" which is 10 years.