With today’s ultra-low yields, it’s safe to say that every income-producing rock has already been turned over. If there were a foolproof way to generate extra income without additional risk, investors would already be all over it, pushing up the security’s price and pushing its yield down. Instead, higher yields are invariably a signal that a security type entails more risk than its lower-yielding counterparts.

Source: Income Seekers: 4 Mistakes to Avoid