Police said on Monday that the man in his late 40s had been placing classified ads for the property in local newspapers in North Rhine-Westphalia since mid-October.
“I've never seen anything like this in my career,” an Oberhausen police spokesman told The Local.
After arranging a viewing with unsuspecting female and male victims, the exhibitionist would open the door to them sans clothing.
Police became involved after several women reported the man and are bringing criminal proceedings for two charges of exhibitionism against him.
Other charges may be added later depending on the results of the investigation, the spokesman said.
Police believe he may have had appointments with others who have not yet come forward and have asked for other victims to get in touch.