Yes you can co -host although that´s not the phrase i´d use. The server host will have the files of the server on their pc, you can use a program like Ioncross Server Operator to monitor the server. To gain access to this program from another pc, you need a program like Real VNC or similar program which allows access to the hosts pc and desktop and then you can use the server operator program just like the host. Depends how well you know the host really...
