Assumed that you operate hotel business in Sumida ward, Tokyo, Japan.
You own 3 stories building and there are 4 rooms in each floor.
Each room does not equip with toilet.
In this case, you need to prepare at least 2 lavatories in each floor.
So, you will prepare 6 toilets in total.
On the other hand….
Assumed that you operate hotel business in Shinjuku ward, Tokyo, Japan.
You own 3 stories house.
When you accommodate guests, a group (they may be family or friend) uses whole house.
They do not share the house with other customer.
In this case, as far as there is a toilet in one floor (ex. 1st floor), it is sufficient.
You do not need to prepare a toilet in 2nd nor 3rd floor.
(it differs depending on capacity of your prospective hotel)