Best setup for a 5 foot sinaloan milk snake

[Arachnaeoccult]

...I'm pretty sure its a sinaloan. I'm buying a pet from lady who no longer wants it. After searching around the phone numbers for a person that might possess milk snakes I found a pet store woman who owns one personally and wants to sell him for 100 dollars. Says he's really healthy, five feet long, and eats medium rats.

My ball python is too fat for the old Tarantula hide thats been sitting idle but the milk snake might have a better chance getting in. Now the baby corn snake is being moved to a smaller tub closer to the width of a five gallon. This milk snake has been living in a 10 gallon enclosure but since the care sheets recommend 2 hides I'm debating on another 20 gallon long tank. Two hides would leave only a small middle space for the 5 footer, unless thats normal?