Pet Saltwater Sharks Pet Shark Question??

Pet Shark question?? - pet saltwater sharks

I think some small sharks, like a ball, red-tailed or rainbow. u can have two each in a tank together? How big a tank for 6 of these fish? Sharks are soooo cool, but I have no money for a saltwater shark I have kind of route is broken go. One last thing I freshwater fish in the tank of sharks or wat?
Thanks