All 3 of mine are pushing 24" atm.. and i've had them less then a year, and would guess their age to be about 1.5 yrs old.. I got them about the same size as that one. prolly abit smaller in the 9" range.. I'de make sure the LFS selling it didn't just buy it from the distributor WC at that age. They can be abit harder to get eating. but are abit sturdier then the juvies from what I've heard of the "baby" eels.
deffinately check out some of the threads. But expect a max size in the 3' range. Also be perpared to potentially ahve a very finacky eater on your hands possibly. MIne only take live, and frozen. and are now on rare occasion takeing pellets. I have earthworms stockpiled ( One of their favorite foods) and I'de strongly reccomend if you do decide to get it also pick up some Prazi-pro and de-worm it as soon as it gets eating well. Some peopel they will eat for right away, others can take weeks. I'de strongly reccomend requesting the LFS to feed it for you before purchase as well. If they say it's eating and has been there awhile.