Which estate agent are you using? There is already a post with the links of the estate agents renowned for their excellent service.
For a furnished apartment, it is required by the law that the landlord stipulates clearly in the contract what's included in the rent or not. Usually, the rent includes furniture, taxes and bills.
However, there might be a charge % processsing fee if you're going through estate agents. Any other additional services (not really hidden costs) like security services and maid service are charged separately.
Hope this makes sense
ps. contact me if you want the list of estate agents, you can't advertise in this section of the forum. I've already posted some links in the Introduce Yourself Section.