I want to buy some nfl jerseys and resell them in a store. Where would be a good place to find information on how to legally do this?

is there somewhere that i can find more information about this?

If the seller claims the merchandise is licensed is it my responsibility? where can i find information regarding these laws?

What are the laws pertaining to selling nfl team logo gear? IE- if i buy a knockoff from china and sell it as a knockoff is it illegal?