How would you make it "atomic", unless you have a cash deal; which is rare and likely nets you a worse price (at least in the US).
In NY, the standard is roughly that after signing a contract the buyer writes a check for 10% of the purchase price to the seller's attorney in escrow. This is typically done after a home inspection, but you still have mortgage and potentially other contingencies. If the buyer backs out for a reason not stipulated in the contract, the seller is entitled to the 10% escrow as damages - but that is not going to happen without litigation. If the seller tries to back out, the buyer will have a lien on the property.
Every state and every transaction can be different, but once you get far enough along, it is generally in your interest to have the deal close. If not, you're going to start a months long process pretty much from scratch.
Someone asking for an addition though would be well beyond what is reasonable; and I can't imagine any seller actually agreeing to that.
In Europe we have laws that make it atomic in effect. The money the contract is signed, the deal is closed, the ownership transfer is made and the money is owed and can be demanded through the justice system if the other party doesn't pay up. Having evidence of the state of the house during the signing of the contract (ideally attached to the contract itself) is enough.
In NY, the standard is roughly that after signing a contract the buyer writes a check for 10% of the purchase price to the seller's attorney in escrow. This is typically done after a home inspection, but you still have mortgage and potentially other contingencies. If the buyer backs out for a reason not stipulated in the contract, the seller is entitled to the 10% escrow as damages - but that is not going to happen without litigation. If the seller tries to back out, the buyer will have a lien on the property.
Every state and every transaction can be different, but once you get far enough along, it is generally in your interest to have the deal close. If not, you're going to start a months long process pretty much from scratch.
Someone asking for an addition though would be well beyond what is reasonable; and I can't imagine any seller actually agreeing to that.