Do you think an online "vip social community" would be a good business idea?

A high fee does not in any way guarantee that the members are above middle-cl, as anyone can fake it though a high fee will keep most people away from the site. There are gold-diggers in this world who would like to do some social-climbing, so you will have to find a method to weed out the genuine wealthy society types from the gold-diggers. There is no sure-fire method to ensure that the prospective members of the site are wealthy, as no one is going to provide you their financial records as proof of their net worth.