It's generally very difficult to get housing for a short period. The few alternatives available are relatively expensive.
The best solution for this kind of a situation is l’Auberge. L’auberge (http://www.colocation-nice.com) offers housing for student on internship in Nice. We offer a housing service adapted to your stay at very competitive prices. Our apartments located in Nice’s centre, close to public transport, the sea and shopping facilities.
Visit http://www.colocation-nice.com to check out available apartments.