"But tax deduction for interest for loans should exclude for established houses."
Interest is an expense so it should be tax deductible. It is irrelevant whether the property is new or old.
"Renters don't get any tax deduction for renting."
Nor should they. If you are running a business then expenses are deductible as in the future there is an expectation that the business will be paying tax. In the case of a rental property that may be from the income from rent in the future when the property is earning more money than the expenses i.e. positive geared or when a property is sold for a capital gain.
