Unless I'm missing something, what do they get out of it? This isn't Europe -> NBA. Is there a transfer payment that I'm not aware of?
If he wants the opportunity to train with the team it could be unpaid and in an unofficial position. He's not there for the money because he doesn't need it. What am I missing?
I don't know the details, but maybe Darren was a bit iffy about signing (study and whatever) and the coaches thought "meh, #14 isn't going to challenge for court time because we're deep enough as it is, we'll offer to put Marcus in there and see what he learns. no one else really grabs us anyway"? Darren thinks, "it's a good chance for my brother, why not?".
e.g., a bit of nepotism, but not necessarily about money.
Remember, they've picked 14 when other clubs are picking 12. That's two freebies. And even then, #13 is a scrawny shooter. Now #14 is a scrawny athlete.
Campbell, IMO, is too small. The one I'd consider is Molitor, but maybe it's a year too early for him and you'd think he'll head to college anyway. None of these guys were taken to PL anyway. Hambour must've been politics, Madgen to the US, Zorich interstate, Wood back to the US, etc.
Sutton and Dodman are the ones that count.