TRIED ROBIN HOOD
didnt like the fact of buying at market---as the costs went up
First off neither you nor I can naked short. Secondly, only a member firm can naked short. Tertiary, most member firms that trade in sub-pennies have very limited net capital and cannot afford to short stinky pinkies, and just like retail that have margin requirement, banks borrow using the Fed Funds Rate from each other, B/Ds have requirements too.
Market Data 
Markets 
AI
