See rocker, if you see a snake that is in bad conditions, and needs "saving", and you buy it, you are basically telling Petco that you approve of the way they treat snakes, because you gave them money. What Petco will do is take your money and buy more snakes that they can mistreat.
If you go with a breeder, you will get a healthy, parasite-free, feeding, properly sexed baby in nearly any color you can imagine!