1)Is rental income a taxable income? Do I have to submit it for tax return?
Yes. Rental income is a taxable income. Once your property is producing an income you will need to submit an Australian tax return.

2) What costs can be tax deductible.
Many of the costs relating to holding an investment property are tax deductible; these include body corporate costs, council rates, management fees, interest charges on the mortgage, depreciation etc. Depending on the price of the property, the rental income and costs that you have, many investors will not pay tax for many years. You should consult a local taxation accountant to prepare the required returns.

3) What tax do I have to pay for my property? 
Besides the income tax, Australia has stamp duty, land tax and capital gains tax. You can find further details at the web site of the Australian Taxation Office or consult with a qualified Australian Accountant.

4) I have a loan on my Australian property from my overseas lender. Is this tax deductible for me in Australia?
Yes. The Australian Tax Office (ATO) doesn't care about the origin of your loan.

Yes. The Australian Tax Office (ATO) doesn't care about the origin of your loan.

The only thing the ATO is concerned about is whether or not your loan was used to finance the Australian property. If yes, then the loan interest and charges will be tax deductible.