You will get a lot of crap from anyone that has been keeping ball pythons for any decent amount of time about keeping multiple ball pythons in the same enclosure. I will not do that but just simply try and explain why it is not a good idea. Ball Pythons are solitary animals in nature and do not get together except for the purplse of breeding. IN an enclosed space multiple animals will tend to create stress to one if not both animals. There have been a few reports of cannibalism in ball pythons, though this is rare.
My biggest concerns are that feeding issues arise more often when feeding. You will have to resort to feeding outside the enlcosure which most people that have been doing this for awhile frown upon. And the transferring of illness from one animal to another. There is no way to figure out which snake has the runny stool for example. There are many other reasons why not to do it and honastly only one reason ever given as to why, and that is because I do not have anymore space. Then honastly you shouldn't have gotten another snake.
A proper quarenteen should be in a different room of the house. If the snake has mites or respiratory infection or any sickness or parasite sitting next to each other is not enough of a quarenteen to prevent the non-sick snake from contracting the illness. Hope this helps a little. Todd