Collaborating with a client

Hi everybody! I have a client who wants to collaborate with me using rush. He wants to create a project in rush and then have me finish it up in premiere. Ideally, he would also like me to be able to make changes to his rush project. Is there a way to do this? We've tried sharing folders, which gives me access to the proxy files of his rush project, but not the project itself.

Don't know if I'm missing something obvious or if the software just isn't set up that way.

If it isn't, can anyone think of a workaround?

Best,

Andrew