A bit of a late answer but it may help others. I am a mature aged student (40+) who did their Diploma (2014) and is currently doing Bachelor of Nursing. I would check with your education provider because you may be able to credit your first year of Bachelor of Nursing, so instead of three years, it will only take 2. So will cost you less. The cost of the course also depends on the education provider but on average with a Commonwealth supported place it costs just over $6,000 a year. Income of an RN is dependent on what state they work in. HEC/Vet is taken out at tax time but if you say you have a hecs debt to your employer they take a bit extra out so you don't lose all of your return. Hope this helps.
Best of luck,
Kkarmy