Increasing my available storage on my iPhone After I sync my iPhone 5c with my MacBook, assuming all my music had been purchased from iTunes, my iPhone should now have no music and additional storage , correct ?
Syncing your iOS device to iTunes will not necessarily remove music from it.
You can delete it directly from the device going to Settings > General > Usage > Manage Storage (under Storage)> Music, slide the first item "All Songs" to the left and press "Delete".