Where can I mortgage the rented car in Xiamen?

No mortgage. The rented car cannot be mortgaged in principle, and the rented car may be sued by the car rental company. Purchasing by rent is a way of buying a car instead of renting a car, but it is different from the general way of buying a car. Moreover, the contract signed by hire purchase is a car rental contract, with additional conditions such as "how long after the lease expires". Before the lease term expires, the car is still owned by the car rental company, and the renter has no right to mortgage the car.