When will the second-hand house key be given?

This question is written in the contract. Didn't you look carefully?

You usually have to wait for the mortgage to come down. After the original landlord gets all the house payment, he will transfer the house (including property transfer, water, electricity and gas transfer, etc.). You have to hand over the house to you within one week after you finish entering the house. If the original landlord doesn't live in it and there is no room for the tenant, you can negotiate with the original landlord by phone and agree to give you the room in advance, which is also reasonable. If someone is alive, you can only wait until then.