There is much previous discussion about buying off the plan (OTP).
Yes, you do save stamp duty, BUT in my opinion:
1. you pay a premium for them in any case which erodes your savings
2. the bigger the project, the more money you pay to project managers, builders, agents etc.
There can be other issues such as delayed settlements... see
http://www.somersoft.com/forums/showthread.php?t=48534
and getting necessary loans (especially if the market drops between time of your signing and settlement).
For example, you might sign for a $500k OTP deal, looking to fianance 90% ($450k). However, let's say the property market takes a bit of a beating, and by the time the building is complete, the bank valuation comes in at $400k. They will now only lend you $370k, so you need to come up with $130k to settle
(instrad of just $50k)
Further, for unit developments, owner corporation/body corporate fees are not struck until completion, and may be thousands of dollars per year more than forecast by the agent.
So, if you are going ahead with an OTP purchase,
1. negotiate the price heavily
2. be prepared for low bank valuation
3. be prepared for higher than expected outgoings (if applicable)
4. be prepared to wait for completion
Cheers,
The Y-man