Changing the Contract

What is the reasonable amount of notice to give when changing contract terms in California

That was a search I got. Unfortunately for this person, a real estate contract is not something like Lando Calrissian's bargain with the Empire, where Darth Vader was free to alter it at will.

The real estate contract is negotiated until both sides are in complete agreement as to the terms the exchange will be made upon. There cannot be any differences in the terms of the proposed agreement and accepted agreement, or you aren't done negotiating yet.

Once accepted by both parties, the contract terms are not unilaterally alterable by either party. They can, in most cases, walk away from the deal completely if something isn't right, but they can't say, "The deal is still on, but you're paying me $5000 more than you thought," any more than they can tell you, "And I get your car, too!"

Now, if something pops up such that you don't think it's a good exchange to be making any more, in most cases you can walk away from it, albeit with possible consequences for the deposit. In such cases, if the other party wants to keep the deal going, they can offer concessions, but you cannot force them to change the terms of the contract. The same thing holds true in reverse. They can't force you to alter the terms of the contract, but if they're ready to walk away and you want to keep them in the contract, you can offer concessions or ask what it would take to keep the transaction going. If you don't like what they say, you don't have to accept those terms, any more than they had to accept the contract in the first place.

In short, contracts to purchase real estate are two-sided contracts, and are not alterable by any party to it without the agreement of all parties.

Caveat Emptor.

UPDATED here