I don't have a complete caresheet for you, just some of my experiences with these animals.
1. They're definately not beginners snakes.
2. They're quite ophiophagous, therefore they need to be kept seperately.
3. They are quite agressive snakes and they absolutely hate it to be handled. It's best to allow these snakes to have some privacy. If you disturb them too frequently, they go off feed.
4. They are best kept rather cool, very much like the Russian Ratsnake (Elaphe schrencki). Also, they need about 3 months hibernation to reproduce.
I think the King Rat is a great snake to have, but they also can be a little bit of a challenge. You definately should do some more research before stepping in. But if you're up to it, then go for it. You'll love 'em.