There are several different models of buying and selling domain names. Some people buy and hold large portfolios, hoping to sell a few domains each year to an end user who wants to develop the domain for their business. Others buy domains, hoping to sell them to another domain investor very quickly.
A third approach involves buying domains that have traffic and appear to have income potential. Some domainers develop these domains with a content management system such as Wordpress, or Joomla (or even SquareSpace - the system that NameMonetizer uses). The developed domains take advantage of the existing traffic and are monetized with AdSense ads or other ads. The end game often involves selling these developed sites to an interested buyer.
You need to do a little research up front to find thesomains. There are several tools available to help you find these.
Brian Johnson calls these "revenue domains" and he will sell you a set of ebooks and videos that walk you through a system for finding, buying, developing and selling these domains. Brian uses Wordpress to develop his domains and he includes step-by-step instructions. I bought and reviewed his system, and I have found it to be valuable.
Johnson goes into detail about how to tind domains that will bring in revenue and how to use WordPress along with specific plugins to create a site that will bring in income and gain value. When you go to sell such a site you will get a higher price because of its track record of revenue generation.