[nekz]

Just our of curiosity, if he wanted to get out of the deal, could he?

Not unless all sides mutually agreed.

Otherwise, it's a firm and binding legal contract. If he decided to walk away, he'd likely be sued for damages, and the damages could possibly be ordered to be released from the trust that held his deposit (and he could possibly be sued for more than the deposit amount).

Or, the seller could hold his deposit ransom. So, if the buyer put in a $20,000 deposit, the seller could say, "give me $10,000 for the troubles", and the buyer would walk away with the remaining deposit amount, as well as a mutual release from the contract.