Investors & landlords

Thanks for the quick response.  To add to the scenario, pretty much all my mother had was the house/property, so no estate as such.  We sold the property directly to a builder without going through a realtor, 7 months after my mother's death.  The house has since been demolished and a new house has been built on the property.  What would be your best recommendation for getting a cost basis now?  

Thank you!