Contract Changes after Accepted and Signed Contract

It may depend on the State where the transaction took place. Essentially, your lawyer did a horrible job in not catching that part of the contract. The fact that this is a Huge consideration I can't imagine why you didn't see this either. Sorry, but who signs a contract / agreement of this magnitude without reading it? If you gave absolute power-of-attorney (real estate) to the attorney and you didn't sign anything - then he screwed you. Most professionals in real estate carry an insurance policy regarding Error & Omissions. I would confront him / her and go from there. If no satisfactory resolution is provided by this lawyer - it's lawsuit time!
This is inexcusable!

So you listed and sold your house before the contract for the house you are buying was signed? I don't think you have much recourse here, but ask your lawyer.

We are in NY. We signed the contract and signed off on the home inspection on the new house and then listed our house the next day. The sellers and our lawyer also signed the contract on the new house. It just had to go through the sellers lawyer. He made the change after everyone else had signed. And we heard back 4 days later - counting the weekend - that there was now a contingency on the sellers finding suitable housing. Our house sold within 5 days of being on the market.

IF that is not in the contract the day you signed it its's non-bonding, changes after signing must be agreed to by both parties.

Do you have a copy of what you sign first?

Yes, we have a copy of the signed contract

Ok, tell the attorney that you did not agree to the changes and will hold the other party to the contract you signed.

So, when is your settlement day?, If they do settled when contracted to do so,you can file for breach in the contract.

Indeed you should talk to your attorney. However, while I do not know NY law, I would bet that as in most states both the buyers and sellers have several days after the initial signing of a real estate contract to have it reviewed by an attorney, and the contract doesn't become binding until after that period of time has expired. Ask your attorney if the delay by the seller's attorney exceeded the time limit. Please keep us posted as what your attorney says.

The contract you signed is binding on you both. If you can prove the sellers lawyer altered it afterwards you can [a] accept and standby the original contract and refuse to recognize and accept the altered / amended contract [b] you can ask for this illegally amended contract to be rescinded and set aside [3] you can accuse the Lawyer of fraud and seek to have him disbarred [4] you can sue the seller for non-performance and compensation.

Instructions: You must, MUST, keep a diary, every letter, every phone call and every problem caused goes in it. You need to itemise your expenses and unforseen costs.

You need to tell the vendor their Lawyer was their Legal Agent, and they are responsible to you for your costs and compensation. They in turn can recover these from him. You need to 2nd guess what he's going to bounce back with, my guess is "They told you, you nodded, said it was okay, and give your consent to the contract being amended. I'm hoping you do have the original and can prove what you say.

Legal B - you seem to be answering a different question than the one posed by PerplexedNYS. The OP is the seller here, not the buyer. And in New York, both parties have 3 business days after signing a real estate purchase agreement to have it reviewed by their attorneys and amendments proposed. There is no fraud or illegality hinted at here - why do you think there was? When the buyer's attorney amended the contract (within those 3 business days) the seller's options are (1) accept the change and go forward with the sale, (2) reject the change, in which case the sale falls through, or (3) negotiate.