As the subject suggests, Is it possible to have the management network for a 2006 controller be the same as the client network that people associate to, or do they need to be on different networks?
This setup will work fine. Map your WLAN to the management interface and all traffic will tunnel via the tagged/native vlan configured on the WLC/rest of your network.
This will however allow users to access the gui of the WLC so keep your password safe. Also how big is the network that you are overlaying the wireless onto? Ideally you should always segment your network regardless of the size for security.