Our lease specifies we need to ask permission to have a pet in our apartment. We made the request, were asked more information about the type of dog (breed and size) and after we answered (small dog, less than 8kg and provded a couple.of possible breeds), we receive the ok from the owner. However, in addition to being told of course that we would be responsible for any damage the dog may create, we are asked to pay 20 Euros per month in extra rent. No real explanation is provided (except that this is for the use of the apartment and building). While this is not a huge amount, we would not pay extra rent if we had another kid. We also are liable for damages anyway. Is this normal practice? Is it legal? Any advice on how to deal with this?