ooooh the perfect destination for something like that would be the Bamboo Bar in Manly. its the nightclub section of the rugby club. i went to an 18th there not too long ago and decided thats where mines gonna be later this year.
costs are as follows:
bond: 400 (should get this back though)
hire: 400
security: they provide 2 security guards but you pay $35/hour each (so $70 an hour on security) the security do their jobs well, i know this first hand as i was actually kicked out of the 18th i went to hahahaha they dont take any shit)
music: they will offer to organise a dj for you for $200/hour, or you can organise your own. i called up a fella i used to work with who left to start a dj company with a mate of his called "Decked Out", and the two of them are doing the entire night for $300, playing non stop.
drinks: not sure of individual prices but there is a full bar within the joint, but only those over 18 can buy.
if your freinds arent all gonna be 18, ask them to try hook themselves up with a fake ID before hand so they can a) drink with you and b) come out clubbing with you afterwards. wristbands are given to those who provide ID saying theyre over 18 so they can drink, if youre under age, i would recommend either drink a little beforehand (you wont be let in if youre pissed though), carry a hip flask if you can hold the straight liquor. otherwise, be sneaky, its a risk but you can get away with getting over 18s to buy for you, and just drink them on the quiet.
the place holds 200 people, which is always good. im having mine there fo shiz.
pm me if you want ph numbers of either bamboo bar or the dj's im hooking up.
sorry for the long winded reply, but i think everything is in there. good luck!