That sounds more than adequate. The Duet is a very nice little interface/pre combo. I'm not in the hip hop scene so I can't comment on which mics are best, but the SM7 is a solid piece no matter what you're doing.
You can probably save some money and skip Logic if he's truly going to be doing just a track or two of vocals. I've heard great things about Reaper
and it's only $60.
That should be good for now. Ideally he could do some cheap acoustic treatment of the room he'd be using. Hop over to the studio building forum to open that can o' worms