Professionally modelled humanoids, fully textured, for a shooter will probably set you back $1000 a piece minimum. To get really good quality you're probably looking at a much larger investment. That's without any animations too, you'll need to source an animator and the cost for that can vary a lot depending on the type of animations (almost all shooters use motion capture nowadays most mocap studios in Australia cost a crapload to rent out even for a day) how many different animations you need - will also depend on how/if the modellers you contract are any good at rigging or if the animators will need to do that too.
Most individuals you find good enough to freelance with this kind of stuff usually already work for a game studio, or are in-between jobs and will only be able to work on your game part time - I've heard endless horror stories of people trying to manage freelance artists on these kind of timetables.
Generally you'll want to try and source everything though a single company that specialise in this kind of outsourcing, I don't know of any in Australia off hand - I've mostly worked in large studios were everything is done in house. For a game like you're talking about though you're probably looking at around 20K and 6+ months for art assets. 1 month for initial brief and sketches going back and forth, 1 month to iron out quality issues and getting your contractors to produce content that actually works in unity correctly, 4 months for cranking out all the assets.
If you're new to game development I would very very strongly recommend you simply try to scaffold your entire game using blocks/cubes and if you ever get it to a point where it's playable and fun then, and only then, should you start considering contracting extra developers and artists.
Forgive my cynicism, but I teach game design at University and I see people jumping into game development with admirable courage but often they fail to see is how massive a task making games usually is. For example, a game like Battlefield is built by large studio with 100+ employees working 10+ hours a day for years on end. To try and build a battlefield like shooter contracting out art assets in an engine like Unity seems a little crazy, I can't help but think you're overreaching.
I could be wrong of course, but I felt it needed to be said.
Last edited by Drac; 30th July 2011 at 03:23 PM.