The property is an asset, a fixed asset. It is made up of land and improvements (building, etc) so there needs to be two fixed asset accounts in the chart of accounts. You split the total value between the land and building accounts. Land is not depreciable, so there should be an accumulated depreciation account as a sub account of the building.
A mortgage is a loan, in the chart of accounts that means a liability account. Part of the mortgage payment is a payment to principal and interest. The interest portion should post to an interest expense account
A mortgage payment could be what is called a PITI payment.
Principal, Interest, Taxes, Insurance
In this case taxes and insurance are liabilities that get cleared when the mortgage company who gets the payment, pays the tax and insurance bill for you.
Open the chart of accounts and create the needed accounts of each type, then do your posting for the mortgage and down payment if any.
