They are amazing snakes - Usually great feeders, calm nature most of the time, easy to keep and seem to tolerate being held well. They are also very intelligent.
As babies they are active and enjoy climbing. They are nocturnal though, so you won't see them much during the day, and they can be quiet secretive, so if your friend is looking for a snake that he will see out and about alot, maybe crb's won't be the best choice. Thats probably the only down side to them to be honest, but their beauty more than makes up for that
They do loose most of their patterning when they reach adulthood, but have an amazing night time colouration and they do show more patterning at night.
As adults a 4' x 2 x 2 would be fine, or even a 3' x 2 x 2 for a smaller sized male.