The best thing that would be for you if you wanted a snake that got rather large would be to purchase the snake you wanted (Burm, Retic, Anaconda, Rock, etc.) as a hatchling or juvenile. When you get a snake that's older, it's harder for them to get used to your scent and become used to human contact. If it was a baby, the biting wouldn't hurt no more than a pinch (when my female bit me it only felt like a pinch) and obviously it doesn't hurt one bit. Sometimes people can't even feel the bite. So it would have been best to go with a hatchling or juvenile while it's still small. The younger they are, and the more you handle, they may just get used to quicker than a sub adult or an adult would.