Your share of this would be for the period from September to December, say 3 months (the rest would be paid by the seller of the property). So actually, the lender can collect up to 6 months' worth of taxes up front when you go to close your loan. At other times of the year, the lender may only collect 1 or 2 months up front.
The moral? Check with your loan officer and your escrow officer as to exactly how much you will need for your tax impounds so that you know what you are getting into.