First of all, you will be happy to know that Kung Fu was invented by a man from India named Bodhidharma. He brought an Indian martial art with him to China that would later be perfected into Shaolin Temple Boxing (chuan fa) which would eventually be referred to as wushu or kung fu. There are hundreds possibly thousands of different systems of kung fu.
The best thing to do to find out if the martial art is legitimate is to check the credentials and the instructor online at multiple sites.