Will I be charged with an additional cleaning cost?

As long as you return the vehicle under the same conditions of cleaning he will deliver you will have no additional charge, so you should clean it after your externally and internally vacation, emptying the waste water and holding tank (Exclusive and motorhome). If it were not so it can be loaded from the deposit the following amounts as appropriate:

Without external cleaning 20 .
No interior 30  cleaning.
Stains on the upholstery € 150.
Smell snuff € 100.
Should have taken pet odor remains / € 150 hairs.
If using chemical toilet and not returning it clean and ready to use € 30.

If a liquid that does not correspond to the correct oil has been spilled into the fuel tank €600

If a liquid that does not correspond to the correct water has been poured into the clean water tank €600