Why are purchase and sales contracts considered bilateral?

Purchase and sales contracts are considered bilateral because both parties involved in the agreement have mutual obligations to perform specific actions. In such contracts, typically, one party agrees to sell a property while the other agrees to buy it, creating an exchange of promises. This mutual commitment is what defines the bilateral nature of the contract: each party's promise is dependent upon the other fulfilling their promise.

In contrast, a unilateral contract would involve only one party making a promise in exchange for an act from another party, where the second party is not obligated to perform. The presence of each party's obligations makes the purchase and sale contract a bilateral agreement, facilitating a legally binding relationship that requires action from both sides to complete the transaction.