The management of a property incurs costs for the owner. However, in the case of a rental, the owner does not have to bear these costs alone. The costs that arise on an ongoing basis from the use of an apartment or house can be passed on to the tenant. These are ancillary or operating costs.
Which costs are considered as such is stipulated by law, so water/sewage, electricity, electricity for staircases and common areas, waste disposal, heating, green areas and many others are included. The exact agreement is specified in the lease agreement. Accordingly, these are the costs that turn the cold rent into the warm rent.