I am very interested in building a portfolio for income.  I feel as though bonds are daunting and confusing, with lots of variable.  Common stock I understand fairly well.  Preferred stock seems to afford some additional protections above and beyond owning common stock, with the biggest downside I can see is probably the inability to liquidate preferred stock on a moments notice the way you can common stock.  What difference does it make what stock exchange the preferred stock is listed with?  I notice many good companies preferred stock is listed on the OTCBB.  

I really appreciate any information you can share!  Thank You.