The two main reasons for using a call option in real estate are:
1. to control some property while you get a Development Application done and
2. to control property that you intend to occupy or on-sell to others with some form of vendor finance.
We work in the second area and if you'd like to learn about real estate vendor finance in Australia, I suggest you do a search for Vendor Finance here. You'll get an immense amount of reading material in this forum.