A legally binding real estate contract must be signed by all parties involved and something of value must be exchanged. A handshake alone is not sufficient to legally seal an agreement. In addition to signatures, a contract must be sealed with a tangible commodity—such as cash, goods or services.t makes sense to check out the real estate laws in the area in which you do business. A real estate contract can be between a buyer and seller, an agent and broker or an investor and seller, or it can involve any number of parties.