the selection of snakes is good, and you do have the ability to actually see your snake in person.
If you are going to be feeding in a paper bag or a cardboard box, you will have to put the entire thing into the regular cage, as a snake can easily get out of either of those. I use those plastic kritter keepers with the colored vented lids for a feeding tank that you can buy at either Petsmart or Petco. They are secure enough to hold a snake temporarily.
It is pretty easy to get regular ratsnakes to accept prekilled or frozen/thawed food. If the snake has been feeding on live (make sure you ask the breeder), you might have to wiggle it a bit in front of him, but make sure you use tongs, so he doesn't catch your fingers by mistake. After a few times of this, you can usually just dump the mouse into the feeding container. And you might not even need to do this at all.
The reasons that I like feeding frozen/thawed are that you can buy them in bulk at reptile shows usually and keep them in your freezer. No more running out to the pet shop and hoping that they have the correct size mouse and paying a premium price for it. But the best reason is that a dead mouse NEVER bit or killed a snake.
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sue