You have to mortgage the loan to buy a house to the bank, and you have no room book in your hand. The bank has a mortgage certificate, and it will only be used to apply for the real estate license in the housing management center after the repayment is fully paid off.
What you said about your landlord's real estate license is probably because you repaid the loan in advance when you bought it, and then took out the house book and transferred it to you.