Hi Greeny, welcome
I believe $75K turnover is the compulsory line for GST registration, and the moment you expect to earn over this threshold is when it is required to register. Though you can register for GST under this amount.
It's your choice what path you take of course... and everyone will have their own reasons for whatever route they choose. So GST may be OK for you.
But just consider that in your first year you'll most likely be running at a loss. That loss is then offset again in subsequent years - from what I understand - please check for yourself though... and so you will have a decent tax offset right off the bat to get your business started.
I would suggest, and feel free to dismiss it... If I were just starting - I would put 100% of my time and energy into getting customers, learning the business, and learning to become profitable. It can be a difficult path for many, and the failure rate in this line of work is no different than any other new business.
If it's not something that's going affect your immediate business and getting up and running, and learning the business as quickly as possible - I'd put it to the back burner for the moment. You can register for GST at any time, so if it were me - I would lessen every extra load or distraction that wasn't necessary - and just concentrate on building my business for ongoing success, and to get past those first couple of years.
GST - register any time in about a minute. I'd be concentrating 100% on getting the business off the ground and operating profitably as my highest and only priority. Anything else is just distraction.
Just my own thoughts.