With so many people trying/doing exactly the same thing (buy, rent out, negative gear, buy again) where will the market go? The rental market is flooded with houses at the moment, a lot of them overpriced because people need the money to pay off the mortgage.
If rent is so much cheaper in the CBD than the burbs, i think rental prices are going to spread from the cbd outwards and shrink purely because there are so many investment properties & town houses popping up. Especially when a lot of older folks are trying desperately to make up for their lack of super. That plus foreign money snapping up properties... Somethings gotta give in the next few years.