thanks for using Trulia.com to find answers to your questions..
you must be from out of town as this type of question comes from people who lived in states with specifiec state wide rate.. anyhow
the rate changes depanding on which township your new construation is within. please note this is township not town or county of city. as example you might be in Aurora but in Wheatlands township. you need to find out which township your new home is at and google the assocer's office phone number for that township. give them a call and ask how they calculate property taxes. although this is very complicated process in IL. they will at least will give you a good idea about today's rate and possible taxes.
please note all the info you will get will only be good for one year, tax rates changes yearly so what you might be paying today might be very diffrent in a year or two..
lastley, please have a realtor on your side even if you are working with a builder becuase the agent will have your interest and should point out things that might save you money now and/or later.
let me know if you need any help, and ck out my website for refun d specials on new construction homes. thanks.
Option Realty Group
Broker/Owner MBC Realty