Hmmm. Property purchase agreements are rather different in your neck of the woods than mine!

Here (UK) we do have a bit of variety, thanks to devolution and bloody mindedness. I'm talking about English here (possibly Welsh too), rather than British (England + Wales + Scotland) or even UK (England + Wales + Northern Ireland). Wales is actually a bit more complicated than that but let's keep it simple.

Here (England), you advertise a house price and invite buyers. You generally engage one or more estate agents (realtors) I think it is called an "invitation to treat" in legal terms.

... negotiations ...

Once a price is "agreed", contracts are drawn up by both sides and "exchanged". When the exchanged contracts are both accepted, then the contract is binding on both sides. Basically: the Buyer will Buy and the Seller will Sell etc.

I think the US is fairly similar in that you do have to agree to something before it becomes a binding agreement.