You can get by with a 10g tank. I would heavily recommend a rubbermaid or sterilite tub though. They have a better floor area when compared to a narrow 10g tank; tubs are also a LOT easier to clean than tanks!
You just need to make sure that the tub lid closes securely; you can use binder clips or even bungee cords to do this. Snakes can get out of the smallest gaps.
That said, you should read the caresheet for all the technicality on cage temps, hot spot, etc. They say it better than I would and it'd be redundant for me to retype all of that info
I would humbly suggest using newspaper for awhile with a new snake. You can monitor its feces/urate better and see if there are any signs of internal parasites (runny feces.) Aspen is great also; it is all about personal preference.