Once you accept an offer, you and the buyer sign heads of terms, also called a letter of intent. They are mostly not legally binding, except usually for confidentiality and exclusivity. They typically cover the price and how it is paid, the exclusivity period, the conditions that must be met before completion, the scope of the warranties you will give, any limits on you competing after the sale, and the target completion date.
Exclusivity binds you too: while it runs you cannot negotiate with anyone else. Keep it as short as you reasonably can.
Negotiate your acquisition deal
Deal structure, negotiation stages and key terms