What are all the documents/pieces of paper needed?

[Ben Feder]

What are all the documents/pieces of paper needed from beginning to end of the real estate investing process? From the time you start searching for a property, to negotiations, to the time you close the deal, to rehabbing, fixing, renting to tenants, selling, etc., what are all the documents/pieces of paper needed, and at what point are they needed at (what are the documents for)?

This question sprang to me when watching the BP webinar "Maximize Profits by Optimizing Your Rehab & Controlling Your Costs", and the fact that REI is basically "1. People, 2. Number, and 3. Pieces of Paper". What are all the "pieces of paper" needed throughout the whole REI process? Thanks for all the advice and information!