Is it valid for real estate agents to defraud and mislead buyers to sign contracts?

I can't. The power of attorney is indeed issued by the property owner and notarized. The client has the right to dispose of the property. The real estate transaction price is negotiated by the buyer and the seller, regardless of the price, it is the true meaning of the buyer and the seller. The signed contract is legal and valid. No matter what the status of the client is, it will not affect the legality of the contract.