im a single mum (not working) and i get about $1000 a fortnight.... i manage to pay rent (i share with a friend though) buy food, fuel, bills etc and have a little bit (as in $50) left over each week. its not much but its enough to live off.
centrelink online services have a calculator where u can estimate how much youll get.
also if your not working you get cheap daycare upto 25 hrs a week (about that anyway) i have DD in daycare 2 full days a week (to give me a break) and it costs about $20 a day. HTH