What's a legal bedroom in bedroom?

[Scott Kronzek]

I am purchasing a 3 unit property, image below. The landlord was previously renting the 2nd floor as a 1 bedroom, and I'm wondering if it can legally be a 2 bedroom? The kitchen and bathroom are down the hall at the bottom of the picture. So, for someone living in the potential 2nd bedroom to go to the bathroom or kitchen they would either have to walk through the first bedroom or walk through the common staircase area. Thoughts?