Personally, I would stay away from the pet stores, personally experience talking here, the snakes there are very over priced, often badly looked after by the pet stores, so badly in fact that even if they got healthy snakes when they came in, by the time you buy them, they are far from healthy, and finally the pet stores often get sickly, genetically weak stock that has been sold to them cheap from questionable sources.
I tell you this because I have purchased 4 corns from 3 different stores in 2 different cities, totaling a purchase cost of $680 before taxes.
Of those 4, 3 had been very ill prior to my purchase, but as is often the case with snakes, there were no outward signs. There were multiple vet trips/medical bills and medications to try to keep just one of them alive. 2 of them died before they could be helped and luckily the 4th, so far seems to be ok.
All in all, if you add up purchase costs, travel costs (herp vet is 1.5 hrs away, one way), vet costs, money wise, pet store corns have cost me $980 for 3 dead snakes. And countless hours of worry, extra care and heartache at the loss of each one.
I knew all the main things to look for, mouth sores, un shed skin, mites, kinks, retained eye caps, obvious sores or injuries, firm body, good muscle tone, ability to slither properly, frequent tongue flicking, poo in viv is not runny or smelly, ect.
Because snakes are masters at disguising illness for long periods of time and then "out of the blue" seem to fall ill, the one that was purchased from stores with 30 day guarantees, the guarantee was no good as he got ill after 30 days and the other two, that store would not guarantee either.
What I have since learned is that a good breeder will help you out if problems arise, many will often replace an ill animal, and they always make every effort to ensure the animal is feeding, and growing, and appears to be healthy. They keep their snakes in proper husbandry conditions.
All around I will from here on out, push people to run, run fast and far from purchasing snakes or any reptile for that matter from a pet store.
Just my experience, and many other's from what I have read!
