That's a very low rate for the role. A friend of mine proofs & edits reports for AU$150 p/hr. Do you need the work? What do you think it's worth? You need to work out what you need to earn, to include provision for super, workcover etc in addition to taxes.

I personally wouldnt do it for that rate. Work out what you want, double it and negotiate from there. If you pretend it's a game or you're negotiating for someone else, it makes it easier. But do the maths first. Also, do you need to register an ABN and a business name?