U have to pay the whole shitload of fees - compulsory union fee plus the course fee of $15 000 plus but im not sure whether u can split it into semester blocks. If u don't have the money u can apply for FEE-HELP up to $50 000.
Essentially... you have to bring 1 semesters worth of fees for the units your sister wishes to do for the first year (each unit is priced differently).