As an exchange student at the HdM, you won't have to pay any course fees to the Hochschule, though you will be required to pay a contribution to the student union (Studentenwerk) of about €70 per semester.

In our experience, living the life of a student in Stuttgart will probably end up costing you €700 a month. This is the collective cost including the accommodation (€290), health insurance (€70), food, clothing, mobile phone, culture/tourism, hobbies (€310) and the costs for public transport (€25).

Add to that the cost of joining in some of excursions, as you'll surely want to see the sights of the nearby cites!