Hello and welcome. I hope you enjoy your new friend...retics are definitely a fascinating snake species, very full of character. Be careful about the feeding response though- they can fly out of the cage when hungry and hit whatever is in front of them. At 9 feet in length, he should be eating an appropriate meal (2-3 jumbo rats or one 3-4 pound rabbit) every other week. No need to be feeding weekly. Retics are supposed to be rather thin, and all too often people overfeed them in captivity, which is not good for either the snake or your wallet. A 9-footer should weigh around 40 pounds, and be about as thick as a 2-liter soda bottle. If you can see the spine, the snake is too thin; if not, he is a good weight. Don't overfeed him- you'll end up with a giant that's lazy, prone to respiratory issues, and will most likely not live to his full lifespan potential. Do post pics- we love pics here
and read a lot and talk to others who own them. A retic is a hefty commitment for a first snake, but not unmanageable if you use common sense. Best of luck.