Q: Create and submit an iBook on behalf of the author?

I'm trying to find some clear answers to this but have come up short. I must be looking in the wrong areas. I work as a tech consultant for someone who runs their own business. I've developed a website for them and am also their Apple authority as he is fairly removed from technology. At one time in the distant past, he authored and illustrated a small (physical) children's book that he would like me to submit to the paid iBooks store on his behalf.

I'm sure there's a ton of legal topics that come up but in the end, is this against any terms of service and/or would this require him signing over specific book rights to me in order to do it or does Apple allow this kind of arrangement? Surely, I'm not the first person to be asked to this for someone...

Thanks for any help you can offer!