Let's say you are a Residential based WISP. You don't really want to sell VoIP, but you notice streams of it on your network already. You have a couple of choices:
Option 1: you can get into the affiliate game with RingCentral, FreedomIQ, Packet8 or other VoIP Provider.
Option 2: you can offer your clients Skype equipment - headphones, handsets, devices, etc. In addition, you can hold classes on Skype.
Either way you make a couple of bucks without the hassles of being a VoIP Provider.