Korean ratsnakes are nice, hardy reptiles, that just haven't taken off in the reptile trade industry yet. Kinda reminds me how kenya sand boas used to be. They were around, but there was really no popular demand for them.
Anyway, one thing I've noticed about hatchlings and juvenile Korean ratsnakes is that they sometimes won't eat what you would consider normal sized prey, compared to other ratsnakes. So, if your friend has any trouble feeding it, try feeding it slightly smaller prey.
Also, i've heard from a lot of people that these guys are like really wild eaters, however, both of mine were really shy. I had to leave food in there overnight etc, and it'd usually be gone. After getting about three years old, they now both eat regularly sized food and aren't as shy about eating while someone is in the room with them.
They have made it through all types of temps, from 50 degrees in hibernation, to 98 degrees in the hottest parts of summer, with no problems. I've never had to use heatpads or lights with this species.
As far as behavior is concerned, they seem to be pretty hyper, always on the move when they are out. If they're held frequently, they will stay pretty good pets.