I have a question along these same lines. I'm in the process of setting up a similar workflow and I'm wondering if there is any way I can move all of my existing pictures and my current LR catalogue from my iMac hard drive to the external drive without screwing up all of my edits. In other words, how are the edits saved in the catalogue? If the location/path of the source file changes is the catalogue smart enough to still apply the edits to the file in the new location on the external hard drive? Or, am I better off just leaving what I currently have on my hard drive there and starting a new catalogue on the external hard drive for all of the pics I start saving on the external from now on? Hope this makes sense, and I apologize if this is considered hijacking the thread. I just figured it was so in line with the content of the thread that it should be okay.

If you move the catalogue to the external drive along with the pictures nothing will be lost. The pictures must be moved from within LR. the catalogue will be moved manually, then you will have to help LR to search for the catalogue. Once this is done, provided that the External is connected, and LR can find the catalogue, there wont be a problem.

Of course if you are only using the main computer to access the picture files, (not two computers) then it will not be necessary to move the catalogue.