You need a valid Type B driving licence (Class D in the U.S. or Class G in Canada) to drive a motorhome weighing up to 3.5 tons in Germany. To drive a larger campervan weighing over 3.5 tons, you must obtain a B96 extension or have a Type C or C1 licence.
You must be at least 21 years old to rent a campervan in Germany and have at least one year of driving experience. If you aim to rent a larger vehicle weighing over 3.5 tons, you must be at least 23 years old.