hehehe The fact that you stated that you are after it just to shoot in your garage will never secure you a shooters license , as it is illegal too discharge any firearm in a designated built up area (assuming you are)....
The only way you are able to get a shooters license these days is to prove that you hunt (or intent to hunt) by written consent by a farm owner . Otherwise prove that you are (or intend) to shoot on a range i.e. by being a member an approved shooting range or being a member of SSAA (sporting shooters association of Australia) .
Once you have the reason part of the requirements , you need to then sit the standard license test for either an A or A+B license .
The license test is very easy (basic gun safety really) its the same test for a 12-year old to get a shooters permit as it is to get a full license at 18 years .
(assuming its still the same).
I used to own a Gamo 440 hunter in .177 (when i was young) It was very accurate with or with out a scope mounted . i used it for anything from targets to shooting small game ... was very potent on rabbits , feral cats and even foxes up-to around 40 meters or so depending on the ammo used ...
You can pay anything from $40 to a couple of thousand on an air rifle , I think i payed around $350 for the one i had ...
In reality with buying a new air rifle , there not the old piece of shi# that you could shoot your mate in the ass with at point blank range and at worse leave a bruise ...
With the majority reaching velocities of around 1000 fps and more ... only around 200 fps off a .22 rim fire ... there something that you hope not to be shot with ...
hehehe ...