"My major is Business finance, and I came across with two professional organizations that caught my interest. The first one is the American Bankers association (BAB), it was founded in 1875, and it is the largest banking trade association in the United States. The BAB represents, regional, small, and large banks. In addition, it offers an broad range of beneficial consultation to all its members, focusing in fields such as staff training, capital management, insurance, risk/compliance, and asset management. Also, I am certain that this is a real organization because I visited their website and learned a little of its culture and values.

The second organization is the American Finance association (AFA), which was founded in 1939. The AFA currently has eight thousand members, and it is the premier academic organization devoted to the study and promotion of knowledge about financial economics. Its purpose is to improve public understanding of financial problems, to encourage the study of finance in colleges and universities,to provide for the exchange of financial ideas through the distribution of a periodical and other media, among others. Furthermore, this is an actual organization that has a website from which you can become a member at different rates." 

Response to other people should discuss whether you think their professional organizations seem legitimate based upon what they've written about it.