Robbing is an easy thing to stop, just provide water, and close the entrance with screen for a day, or put on an entrance reducer. Make sure there are no holes in the hive bodies, etc. Also remember that you can make sure to create good habbits in this new beekeeper by helping him learn to inspect for brood diseases, mites, etc. That way you can help insure the safty of your hives as well as his. Help teach him those habbits right from the start to aviod future problems, and he is likely to welcome the help in learning.