The bank will tell you how your shares are doing. Ralf Schumacher, the penetratingly grinning guy from used car advertising and a former racing driver, knows what your car is worth. But what about the value of your apartment? You can estimate the basics yourself, as long as you are confident enough to do a little arithmetic. A real estate agent will help you with this.

Anja Wolff, 57, is the owner of a real estate agency in Wetzlar. In the small town in Hesse and its surroundings, it primarily sells single-family homes and condominiums. As an expert in real estate valuation, she often has to deal with the question that concerns many owners: How to actually convert stones, roof tiles, lawns and a living room with a view of the countryside into euros.