1, commercial loan. If the purchaser borrows money from the bank to purchase a house, when the loan cannot be repaid in full as scheduled, the bank brings a civil lawsuit to the court, demanding the purchaser to repay the mortgage by auction.
2. Private lending. For example, Zhang San borrowed money from Li Si and agreed to mortgage his property to Li Si, but he could not repay it at maturity. According to the law, Li Si can't directly obtain the mortgaged property, so he can only sue Zhang San for repayment, and then he can apply to the court for auction of Zhang San's property in the execution stage. If the property is not mortgaged, it belongs to Zhang San, and the court can also auction it.
3. Judicial confiscation. In criminal cases, there is a judgment to confiscate all personal property of the criminal suspect. If the real estate involves real estate, it can be auctioned according to law, and the realized money will be returned to the state treasury.
4. ownerless property. That is, unclaimed property. This can also be auctioned, and the proceeds from the auction are nationalized, but it rarely happens in real life.