The types of mortgaged houses accepted by most banks in our country do not include secondary mortgage, because your house has never been paid off, and you just paid a down payment, for example, the total price is 2 million, you paid a down payment of 500,000 yuan, and there are still 6,543,800+0.5 million yuan, which you have not paid back yet. You don't own the full value of this house, and you don't own the full ownership of this house, so you can't use this house as collateral. Mortgage is the full value of the house, and the bank will give you a loan according to the full value of the house and the market situation, but obviously you don't have full ownership of the house now.
If you really need money now, you can compromise. For example, you have bought a house for several years now, and then you have paid off part of the loan, leaving about 500 thousand in the loan. In this case, you can borrow some from your relatives and friends and pay off all the bank loans at one time. By this time, you have settled all the debts owed to the bank, and the house is entirely yours. At that time, you can use this house as a mortgage loan to the bank, which is also possible, because you have paid off all the debts owed to the bank and the bank will mortgage it to you. Although you took the compromise route, you finally got the money.
In the transaction between individuals and banks, banks always have the upper hand. No matter how smart you are, you are not a bank, because people are good at investing and managing money. If the bank didn't even know about annuities and profits, it would have closed down long ago. Banks spend so much money every year and invite so many experienced professional investors. This must be clearer than you, so it is impossible to say that there is no need to consider creating loopholes in banks.