Retailers usually squeeze you for price, pay slow, have tough return policies and if it “ain’t” selling will ask for markdown money. Slow pay part can be the toughest. They may say 30 day but it can run 60 or 90 days.
They may want to know if you company is financially viable. They should not ask you who your suppliers are to try to reverse engineer what you are selling.
Anybody run a D&B on Costco? I doubt that it pays “late,” unless it’s heading toward bankruptcy or something else I am not aware of.