Imac laptop

some guy gave me his imac g5 with 30gb hard drive to figure out how/what is taking up all the space.  There is 3gb left out of 27.8gb.  He wanted me to delete all the extra apps that came with it but I don't think its worth the time.  How much space does an OSX install take?  Do multiple profiles affect the space (i.e. duplicated shit) I've never used OSX before.

>>1
Multiple profiles?  How many?  Does he create new users every time he forgets a password?  Don't laugh because I've run across users that do. If he's the only user delete all users files except in root admin and one other.  Then change the admin password and DO NOT GIVE IT TO HIM.  Give him a user password for the one remaining profile he can remember.