What is the opposite of heritage?
Solution 1:
Legacy
"A thing handed down by a predecessor" - OED
Solution 2:
I like Chris's suggestion, "legacy", but another synonym that fits might be "bequest", which is defined in simple terms by Merriam-Webster's Learner's Dictionary as
the property or money that you promise in your will to give to another person or organization after you die
Solution 3:
"Something left by the subject to be inherited by someone else" is called the estate, especially in legal documents.
E.g. The late Mrs A's house is part of her estate