Although a document may be valid with merely a signature, it may not always be acceptable by today's standards for verifiability.
When it comes to agreements, there is nothing more powerful than a signature on a piece of paper. Ever since parchment and ink were invented, signatures have been used to make agreements legal. Although a document may be valid with merely a signature, it may not always be acceptable because today's standards lend as much importance to verifiability as they do to legality.
Follow the Law
Make sure the language or content of the agreement doesn’t violate federal or state law. Any provision contained within an agreement that violates either party’s civil rights or any other law or statute would be considered invalid and unenforceable. If you have concerns about possible violations, contact an attorney or legal aid for advice.
Sign the Agreement
Have the agreement signed. The signatures should be acknowledged either by two witnesses or a notary public. Notarization and witnessing are methods by which the parties who are relying on the document can verify its credibility. Some states don't require witnesses for an agreement to be legally enforceable, but an agreement claimed by someone to bear a forged signature would be highly contestable in court if it's not witnessed or notarized.
Some documents, such as deeds, may require notarization with specific state language to be acceptable to title companies, attorneys or other parties relying on the documents. Although a deed or agreement may be technically legal with a witnessed signature, it might as well be an illegal document if it is unacceptable to those who are involved in the transaction.
Record the Agreement
Record any agreement or contract to buy and sell real estate in the real property records of the county or jurisdiction where the property is located. This is particularly important if payments are to be made over an extended period of time and no actual deed will change hands until the price is paid in full. If a seller signs a written agreement to sell you a parcel of land and the agreement remains unrecorded, he might deed the property to another party in the meantime. If the state is a “race-to-the-courthouse” state, the purchaser named on the deed will have acquired the property and your agreement will become invalid or not legally enforceable when you try to acquire the real estate. You may still have rights to sue for breach of contract, but odds are that you will be unsuccessful in acquiring the real estate.
Confirm that the person signing the agreement has the authority to make it. If he signs the agreement on behalf of his corporation, LLC or other entity but he doesn’t have proper authority to bind the company, the agreement may be unenforceable.