House size for a dwarf?

[Swissgreys]

I am finally getting around to setting up my cage this week, and am super excited.

I still have one question though.
What is a good size house for a dwarf?
I will probably add at least 2 houses to the final cage set up, but am wondering if it is better to have a small house with a potty nearby, or a larger house which can also have a corner potty inside?

Or do I just offer both and see what happens?

I know all hammies are different, but would be interested to hear what others find work for them.
Thanks.