Margin Requirements to short a penny stock:
Brokers require investors to put up collateral to guarantee against potential losses in the form of margin requirements. Often times, brokers will require OTC investors to have $2.50 of margin per share to short a stock under $2.50, which can make shorting penny stocks very costly. For example, if an investor shorted 2,000 shares of a stock at $0.50, you have to have $5,000 in your account. All along, the maximum profit for this position would only be $1,000, if the stock went to zero.