According to the normal loan process, you have to pay the down payment before lending, because the bank will handle the loan formalities for you only if you know that you are able to pay the down payment. When you sign in person, the bank will ask the buyer and the seller to sign the "down payment receipt certificate". In practice, most of them also pay the down payment first, and then go through the loan procedures. Of course, if there are special circumstances, buyers and sellers can also go through the loan procedures first, pay the down payment and then transfer the ownership. But I suggest you take out a loan to buy a second-hand house. It is best to find a regular second-hand housing brokerage company to help you with the relevant procedures. First of all, it can control risks for you. Second, ordinary real estate brokerage companies can supervise funds, so as buyers, they don't have to worry about down payment, and sellers don't have to worry that buyers can't pay down payment after cooperating with relevant procedures.