When you decide that you want to purchase a piece of real estate, whether residential or commercial, your attorney or real estate agent will prepare a document called an offer to purchase. This document will contain the date you are making your offer, and a description of the property you are offering to buy, as well as your offer amount, the amount of your deposit, your intended down payment, and financing terms. It will also include the name and address of the seller, any proposed conditions of your offer (such as a request that appliances be included in the offered sale price), and several other provisions. Your attorney or real estate agent will ask you to sign it, and then they will send it to the seller.
You should carefully review the offer to purchase and make sure you understand and agree with it before you sign it, because once the seller adds their signature, it has been accepted and it becomes a purchase contract by which you are both bound. At that point, it cannot be changed unless both sides agree to an amendment. Sometimes, acceptance does not occur until one or more counter-offers have been exchanged.