subdivision/unit development

Hi all
As a beginner, I have a property in north vic and want to subdivide and build some units before selling them off. I am told I should be able to get three units on my block which is just over 700sqm.

The architect will organise the permits which should cost around 15k. I am not sure how much the builders charge per square metre, any help? Some agents told me I am better off selling my house including the permits and plans and let the devlopers do what they do. Which option to take?

Thanks