You of course cannot take the standard land value from the property where the two-family house is located, but from the nearest meadow / field. If the standard land value is based on properties that are built on or can be built on, then the value does not apply to your property that cannot or may not be built on. How is the two-family house used? If rented out in whole or in part, I would definitely buy it, then you can write off something at the tax office and the costs at the notary are the same. Your mother can give you the money back as a gift. Usufruct and right of residence reduce the value by the rent multiplied by the statistical life expectancy.