Suppose you want to set up your directory so that people have to either give you a reciprocal link or pay you, in order for their link to be approved. Here's the steps to do that:

1) Go to Admin Panel -> Listings -> Link Types. Change the name of the regular type to sponsored. If you want both the sponsored and reciprocal types to look exactly the same, remove the
<IF {LINKTYPE} is recip><img src="{IMAGESURL}/star.png" ></IF>
line from them.

2) Go to Admin Panel -> Settings -> Switches and check the "only allow reciprocal and sponsored" box. Make sure the sponsorship switch is enabled too.

3) Go to Admin Panel -> Settings -> Sponsorship and set up listing type sponsorship or member usergroup sponsorship as desired.