Visas for Australian Students are processed through the Perth Consulate and Visa authorisation may not arrive more than 3 weeks before the semester starts. It is possible to get your visa issued elsewhere, such as Singapore, but this is more difficult and will be your own responsibility. International participants should email the Secretariat for information on their status. It is difficult to estimate how much money is needed to cover living costs, as student preferences vary considerably. While living costs in Indonesia are cheap by Australian standards, it is wise not to underestimate cash needs.
Costs change according to fluctuations in-country and according to the exchange rate.
Basically, this question is way too variable on personal preferances and circumstance to answer. There are only provisions within Indonesian visa regulations for accompanying wives and children on this type of visa, although it is usually possible to obtain a visa for accompanying husbands.