That BP is pretty skinny. I'd want to see it eat, and grill the seller on past feedings. If you get a bad feeling or think he's not telling the truth, turn on a heel and bail outta' there.
Also, grill the guy on the snakes history....Like maybe he bought it, can't get it to eat, and wants to unload it. Then again, seeing the tubs set up in the background makes me think this isn't the seller's first rodeo.