Little Cloud wrote:

I think that he means like a promise of sell/buy. For exemple, when u find a house to buy, u can decide to write this kind of pre-contract with the seller and u can define all the terms and conditions of it like the prize, the period of payment and so on. it is useful when u have decided to buy that house but u don't have all the money to buy it and give him/her just a little sum, in general 1/3 of the total. In this case, it's like u promise to buy it and the seller promises to sell it to you but, in case u don't buy the house at the moment decided together, u lose the money and the seller can sell the house to somebody else.

What you describe would be a contract under English law, that is both sides would be committed.

What usually happens is that agents send out details of the transaction that is agreed subject to contract. This is not binding - it is simply information for the parties' lawyers. It is highly unusual for anyone other than a lawyer to draw up a contract for the sale of land; indeed it is illegal for anyone other than a lawyer to do so if they get paid for doing it. If an agent were to do it the course of his business he would be deemed to be doing it for a fee.