How to sell property back to seller after 30 days

I purchased a lot with a condemned house on it from a friend for $27,000. I put down $1000 on it. They are financing for me. I no longer want the property and they are willing to reverse the sale or buy it back from me. What kind of paperwork do we need to do this properly? They sent me a Texas General Warranty Deed with their purchase price being $1500 to buy it back and I was going to notarize it but then I started thinking about legalities and taxes, etc.
Thank you for your help. Lenora