Rather then spend your time on directories, which aren't very useful, I suggest you spend more time on seo and getting links from worthy websites but writing as a guest.
that depents on the where you are buying links. if you are going to buy links from a trusted directory, you may make profit from this
Be very carefull with directories. I am registered in many directories but most are not recognized on SE links (link:yoursite). I believe this is because SE spiders do not follow the entire stucture of a directory, based on different requests from the same URL, unless it is all declared in the sitemap.xml (if SE is google for instance). But this is my own theory only!
PAID DIRECTORIES I expect the large and well known directory owners to promote and link directly to their internal categories and get them some PR and direct popularity. I have one site in one of the most popular directories, premier position, 5 internal links for over a month = not one visitor. BIG DIRECTORY OWNERS promote and external link to your internal pages... The phone book provides traffic and if directories don't send traffic google will remove you because you don't do anything for the net. FREE DIRECTORIES I have submitted to thousands of directories for many sites. Free directories take time to get approved so just go for it I have never seen a penalty. And why should there be? You are placing your self in the various internet directories - that should be done. Why are you not in them already? I give some credence to too fast link building for a young site eg under one year. But when any penalty is lifted you are in thousands of directories with many back links. A free PR0 directory today may be a popular PR 5 in a few months - if google ever updates again http://www.omg-1.com