Making a new lawn takes time. Whether you decide to sow seeds or put them in the grass, the pre-preparation must be done thoroughly. It will be much more difficult to fix things when grass covers the ground. But once this is done, a well-laid lawn lasts a lifetime.
The lawn provides you with an instant lawn and can be laid for a large part of the year. The usual time for laying the lawn is from fall to spring, except when the ground is icy or muddy. Laying your lawn in late spring or summer is risky because it may not 'take' properly in hot weather, and in any case, you will need a lot of water to keep it alive. My advice is to stick with fall. You can also buy turf supplies in Sydney online from https://www.hawkesburyturf.com.au/.
People always think that growing grass from a seed takes too long, as you have to leave it for months while it grows. That's true, but if you choose to sow in the fall, you'll have a perfectly usable lawn in the spring. And you probably wouldn't have wanted to wear it much in winter anyway.
You should need to water a new lawn only if it does not rain for several days after planting or the lawn; do it thoroughly, then leave it in for a few days before doing it again. You should water a new lawn only until the lawn is about 1 inch (2.5 cm) high and the grass no longer lifts if you try to peel off a corner.
For some, tending a traditional lawn is their life's work, but for most of us, it is something we would rather not have to do.