Guidance for Building Granny Flat in Sydney (Blacktown Council)

Hello

Looking for some guidance in Building Granny Flats in Sydney . This is my first experience with building a granny and I am still researching . Meanwhile I thought of posting it here so that I can get some directions from experienced investors/builders.

1. Currently at the looking stage for properties . Looking for 500 plus land . Most of them have Cladding or weatherboard houses in it for dual income purpose. Plan is for me to buy and build a Granny in it . Any drawbacks with this strategy if you can highlight pls.

2. I see the options of Brick Grabby vs. Weatherboard ( I prefer Brick not sure how much difference it would make in cost - analysing now ) . Also any other options worth considering

3. Any recommendations for Granny Builders ?

4 . I was advised to go with a private certifier rather than council . Would be contacting someone soon for more details.

5. I also want to understand at what stage the duplexes are an option ? ( though that is not my current plan , but given some of these houses are definitely knock down in a few years . Would that be a council question or a private certifier ? ( to understand the eligibility/council approvals/DA approval times/ building costs etc ) )

Thank you very much for your time.