I've recently purchased Lightroom CC and am trying to upload my pictures, currently located in iPhoto, from the master file on my hard drive. Is this an issue since the photos are currently in the Apple cloud?
It shouldn't be as the two clouds are separate and distinct. The files will exist in two places on your hard drive until Lightroom CC syncs them to the cloud and purges them after. The masters from iPhoto will remain until you delete them.