My mother wants to buy a property. I want to help her and give her some money. Will she pay tax duties?

It depends on the amount which needs to be paid. There is an allowance of 100,000 euros when the beneficiary is an ascendant (mother or father) of the donor (art. 779, I. CGI). This means that no tax is due when the sum donated does not exceed €100,000 over a period of 15 years.