Great choice of car to buy. I bought mine for $2000 but be weary the cheaper they are the more repairs. I know this after having a LC torana, a TA22 celica (highly modified) and now my AE82 hatch, with rust.
Heres the low down, be prepared to spend about $5000 for one in good shape. Or one cheaper thats slightly bumped, or rough.
Cause your in Melbourne, maybe also look towards SA as well, they be cheaper to buy there.