While I haven't been to Morocco for over 2 years, phone service for locals in non-industrialized nations all over the world tends to be cheap phone, available locally, with prepaid sim cards that you reload. It depends a great deal on what services your friend wants and can they, for instance, do without data and use the wifi in their accommodations or will they go to pieces without having it all, all the time. If that's the case, I can't help and will be expensive, all things relative, I suspect.
My cheap unlocked phone was purchased years ago in India and works just fine for all my travels, everywhere in the world (except in N. America and on ships). My advice would be to email their first accommodation and ask about availability of inexpensive phones and sim cards. I already had my phone and a friend in Fes picked up a sim card for me from a corner store.
Rentals will likely be the most expensive option. Buying a phone and sim before they leave will also be pricier than waiting until they arrive in Morocco.