Sydney home and land packages

Can anyone shed some first hand light on home and land packages in Sydney?
We are not first home buyers but really have no idea where to start with this.

Have done some googling and found, within our price range ($700 Max but under $650 would be ideal!), some places in the South-West at Oran Park, Spring Farm and Gregory Hills.
* Any feedback on these areas/ other suggestions of places to look?
* A lot of them say "all inclusive/fixed price building contract" but I'm sceptical. What do we need to look out for?
* How does land registration work and what does it mean? Have seen a few different descriptions (land registered/ not registered / registered until certain date, etc)
* How long does a new build take?
* Any other advice?

Thanks in advance!