If it is already on two lots, the only thing you need to do is lodge a form (I forget which) to create the second title. The form you need is Queensland Land Registry Form 14 - General Request Form.
This costs about 300 bucks.
Council contributions etc are not required here.
There will be other smallish costs for demo/house removal applications etc and service abolishment (gas elec telecomms etc).
The biggest costs (for land prep) will come from servicing (sewer and water) from QUU.
House removal/demo will be a biggy but not necessarily as bad as you might think. Our last quote was 10.4k for a not insignificant house, with some asbestos within.
Cheers,