There are usually three phases to any copywriting job: drafts, revisions and project completion.
The draft, which may require interviews and additional research, will be submitted for your review and input. Once you see the words on paper or, more accurately, on a Word document, you may very well have some suggestions for additions, edits or rewriting.
You would then receive a revised copy for final approval. Once the recommended changes are made and your approval given, the job has been completed and it is your intellectual property.