Nearly everyone qualifies for the "automatic" home owner's exemption from cook county regarless of the dollar amount of taxes. The percentage decrease you will be allowed is unknown but between 0 and 25% in the actual reduction. Assume 10% to be safe. More is just icing on the cake.
Since this home is newly constructed and not yet sold to the first owner, the current taxes are reflective of a property once attached to this lot. Now there is a different property built on the same parcel of land. Depending upon the classification of the property etc that occupied the lot prior to this new home being built, the taxes for you as a buyer could be higher or lower. Keep that in mind as well. 1.5% of the purchase price is about average to estimate what your actual tax bill may be. I personally would not even use the $7700 figure unless the PIN on the assessor's website matches the PIN recorded/listed on title to this new purchase. If that is the case (which would be the first ever in 8 years of experience that I have seen), then the $7700 is correct. Most likely, there is no PIN even issued for the new parcel so utilize the 1.5% factor. This is what we use as mortgage underwriting criteria for loan approval industry-wide so you can't go wrong either way. If you have any further questions or need additional guidance, please visit me below. Hope this helps.
The only thing that I'd add to Wayne's comments is that you may not qualify for the homeowner's exemption until you have already lived in your new home for at least one year. You can verify exactly when a new owner qualifies for the exemption on either the Cook County Assessor's website or the Cook County Treasurer's website. Good luck.
Broker Associate, Sudler Sotheby's International Realty
If you live in the home, you will qualify for a homeowner's exemption. If you're a senior, there is a senior's exemption and a senior freeze. You should also check to see what exemptions are already applied.
Because the house is new construction, be wary of the current tax bill. If the taxes are based on what used to be there (i.e. old teardown) they are likely to spike with a new home on the property.
Typically buyers of new construction in Cook County see there taxes calculated at 1.8-2.0% of the purchase price. Talk with your agent or attorney. Ask them to look at the tax history and see what the taxes are based on and what exemptions are already in place.
I attached a link to the cook county assessor's site. Use their Online Tools tab to look up the property and get the tax history.
Best of Luck