Second Home Cost basis given as a gift (from a house that was built by parents)-Capital Gains

I sold my second home last year.

This home was originally built by my parents back in 1986 (I lived in it as well back them) It was Gifted to me in 2008.  There are NO records at all anymore from when they built it, other than what the Property Tax department has (date my name was put on the deed and I believe the tax bill showing housesite value).

HOW do I determine the cost basis??