How would I find out how old my Chicago 6 flat condo building is?

tickle

You should visit the town centre of the borough where it is. Their records, for tax purposes, will tell you when it was built.

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JudyKayTee

If it's a condo your Attorney reviewed the title search and in many areas would have provided you with a copy.

Have you checked it? That's a start. So is your Attorney as well as the condo association Attorney.