Once you`ve found someone to buy the used Stephen Curry mouthguard you found near the Golden State Warriors game bank, or if you`ve finally found someone to sell the mint green Ford Mustang you`ve been dreaming of, make sure nothing goes wrong when selling. If you don`t have a purchase and sale agreement, the buyer might mistakenly think that he or she will have a brand new mouthguard or that the seller suddenly wants more money for the car. If you are selling or buying personal real estate, you should consider documenting your transaction in a personal real estate purchase agreement. A written contract allows both parties to carefully review and describe the details of the sale and confirms each party`s understanding of how the transaction will take place. A sales contract is signed during or after the exchange of money and goods.