sentences:  Conversely, if A signs a contract to buy a car from B for $0, B's consideration is still the car, but A is giving no consideration, and so there is no valid contract.However, if B still gives the title to the car to A, then B cannot take the car back, since, while it may not be a valid contract, it "is" a valid gift.In common law it is a prerequisite that both parties offer consideration before a contract can be thought of as binding.