They are NOT prostitutes. Geishas are and always will be highly-skilled entertainers — nothing more, nothing less. It helps to note as well that prostitution is illegal in Japan ever since 1956. In fact, this idea that geishas are prostitutes might have come about not only from Hollywood movies that misrepresented them but also from people who have mistaken geisha for "oiran" (the true high-ranking courtesans back in olden Japan; since 1956, they no longer exist).