In the following video, Motley Fool analyst Andrew Tonner tells investors why he's adding shares of Costco (COST -0.37%) to his Fool Real-Money Portfolio. The portfolio is based on defensive value investing, consisting of stocks that will continue to grow over the years in both strong and weak times in the market. Andrew tells us how Costco's business model has allowed it to continue to grow year after year even through the recession, how it also continues to grow its dividend, and why it's a much cheaper buy than you might think.