Some retail investors tend to love penny stocks (shares in companies trading under $5 per share) because of their explosive volatility and multi-bagger, millionaire-maker potential. However, a low stock price doesn't always mean a good deal because these companies are often cheap for a reason. Let's explore the pros and cons of investing in Chinese electric vehicle (EV) maker Nio (NIO -1.38$4 per share -- as it struggles to differentiate itself in the increasingly competiti ...