60% to 80% of the appraisal price and transaction price of second-hand houses are reasonable. Complete equality is impossible. The evaluation prices of loans and mortgages may be a little different. In addition, if you want to know the evaluation price of second-hand houses, you can go to a professional real estate appraisal agency. The difference between the appraised price and the transaction price of the second-hand house is determined by the house itself and its use. These can be found on the website. However, for loans and mortgages, it is not just a data, but an evaluation report stamped by the company. So pay attention to the distinction. The premise of signing a sales contract is that the buyer and the seller check the authenticity of the signing subject, mainly for the buyer to verify the identity of the owner and the authenticity of the owner's certificate, especially in the case that the buyer and the seller trade on their own and there is no third party as an intermediary guarantee, to prevent criminals from forging the owner's identity card and real estate license for fraud, and to avoid financial risks to a great extent. Whether the house is owned by * * * or not, and if the house is owned by more than one person, the seller shall provide the identity certificate of the owner of * * * and a written document agreeing to sell the house; If the husband and wife have property, whether to obtain the written consent of the seller's spouse; If the house has been leased, the seller shall provide the written opinion of the lessee agreeing to sell it; If the house has been mortgaged, the seller must provide a written document that the mortgagee agrees to sell the house.