All the best in achieving the dream
I haven't done it but have researched a little and talked to 2 that have done it.
Depending where you choose to build (how remote) you may still have to pay rates and possibly still pay for the privilege of having power and water running past your property even if you're not connected.
Check annual rainfall for desired location and what time of year. 100,000 litres of tanks seems to be the minimum norm here in SA.
$60k for off grid solar with a bit of wind power added in that (5 years ago). It will sufficiently run a normal energy conservative household provided you're solar is facing north. But I'm not so sure if air-con is included in the running cost. Regardless of solar a back up geny will always be necessary.
House design is just as important and I don't mean architecturally built. A simple design with keeping the outdoor elements in mind.
For example, 2.5m varanda running around the whole house. Roof pitch and size to minimise heat and capture water. Timber windows with 6.38 laminated glass is far more better insulator than your normal 3mm and cheaper than double glazing. Open plan to allow a breeze to run through the whole house. Size and location of windows to capture as much sunlight in winter. Central heating using a wood fire would great.
Don't build with large trees close to your home. As nice as it sounds it dangerous. Fire breaks around the perimetre of your property and fire protection for your home with an evacuation plan is a must.
The more remote, the more expensive building goods will cost.