We verbally agreed on $24k and are in the process of arranging the CASH sale.

We have the same arrangement with the other rental and even though his name is tied to the mortgage we both are on the hook for it financially from our standpoint (although obviously not from a credit standpoint).

Don't make special arrangements to meet with them to discuss payment arrangements. 

., an LLC) and formalizing the arrangement.

I had not arrange any City inspectors to check the house as the Certificate of Occupancy is not up yet.

Is it an exclusive arrangement?

What ind of arrangement and document needs to be put into place to protect both parties?  

It was a separate page reiterating the pre-arranged payment milestones with a place for the contractor to sign and date which I kept along with the receipts.

I don't want to be shown as a pushover but I also don't want to be too much of a hardass going into it causing animosity because of the shared living arrangement.

@James Watts - if you can get someone to put the money up under that arrangement you described that would be a great deal for you and reckless for them.