Answer: $500,000
Step-by-step explanation:
Even though the property had a cost basis of $1.5 million to Brian's uncle, Sam, that $1.5 million basis does not automatically transfer to him.
Instead according to "U.S.C. 1014 - U.S. Code - Unannotated Title 26. Internal Revenue Code 1014. Basis of property acquired from a decedent", the basis that will be passed to him will be the Fair market value of the property upon his uncle's death.
The property was valued at $500,000 when Uncle Sam died so that is Brian's basis in the property.