First rule, don't buy one house. You will never get ahead, not quickly anyway.
Buy 2. A place to live in, and an investment house in a high growth area. Atm, SE Qld, and WA are probably your best bet. In these areas, they tend to double in value within 5years.
Pay interest only. The ammount you will make from the second home, will pay off your first, if you structure it correctly.
Remember, as everything else increases, so does the rental income, and tax benefits from having the investment property.
The loan structure is the most important aspect. If you get this right, you will get a tax break, and also, everything on the investment house is tax deductible.
The rental income from the investment house, should pretty much cover its interest payments anyway. So you will have a mimimal outlay for it.
In time, hopefully you will either earn more, or spend less. Allowing you to pay more off your primary residence. Therefore reducing the minimum payment each month. In 5-7 years, your investment house has pretty well doubled in value. You could sell it, pay off the majority of your primary residence, or you could borrow against it and purchase another property. All depends on your financial situation at the time. Either way, you'll be alot further ahead now, than you ever were.
Whatever you do, DO NOT GET A PRINCIPLE AND INTEREST LOAN. Its a sure way to ruin your lifestyle, and limit your ability to make any real money.
Think of an interest only loan, as a large credit card. You can either pay the minimum each month, which will stay the same depending on interest rate fluctuations, or you can pay more, and reduce the minimum payment each month. The choice becomes yours.