I haven't finished reading all of the replies, but I don't get it. It's his album. He's producing it. He's written it. You're facilitating the recording buy letting him, for a fee, use your studio. Why is this even a discussion? Why are you attempting to wear all the hats? As far as I see it that is beyond your role. I mean REALLY beyond your role. So much so that if I were said artist, it would pss the hell out of me. I haven't finished reading, but so far I haven't read anything that says you're the producer or have been asked to produce. His drums loops are his and his artistic vision is his alone, not an engineers and not a studio owners.
But you know, people are different. I could be entirely off base . . .