the basis

Delinquent property taxes (from periods prior to the owner inheriting the property) when paid by the new owner of property, add to the cost basis of the property.  You can only deduct as an expenses taxes that were incurred during the time of ownership.

So for inherited property,  generally,the Basis  of the inherited  property is the Fair Market Value on decedent's death ( or FMV on the alternate valuation date if elected.)

Add;  previous delinquent taxes paid, attorney fees, commissions, home inspection etc