Receipt from sale of property, inherited from a relative will not be included in the national income as receipt from the sale of such property is by virtue of transfer of an already existing object.
The transfer of an existing property is considered just a transfer of ownership from one person to another.
Only the very first sale of an asset is considered as factor income.
Adding the receipt of a second sale of an existing asset will lead to double counting.
Thus it will not be included in the national income.