Next generation search engines will examine the relevance of both your incoming and outgoing links as part of their search algorithm.  If you're sitting there with just incoming links, your search engine performance will gradually deteriorate.

Remember, it is not the "number" of links, but the number of "relevant" links. 

Anchor Text:  Don't just create a "link" - create relevant words that have an imbedded link in them.  For example, don't create a link that says, http://www.yoursite.com.  Create one that says, Charlotte NC real estate, with the link imbedded.  This helps determine relevance. Don't worry about agent names in links.  Consumers don't look for agents by name - real estate is "local."