Difference Rental: Bedroom vs. Unit

[Collin Miles]

Hello BP Community,

I recently moved to Baltimore, MD and my first day I began looking at the property around me. In searching I found a 6 bd 3 ba brick structure that looks abandoned. I am going to send a letter to the owner however I have some questions before I do that. 

   I know 5+ units is considered commercial

What is considered a unit? Would this purchase make me a commercial real estate investor? 

Depending on the replies, I have thoughts of turning it into 3 livable units separated by floor. Would that change anything regarding the purchase of this building?

Unit=own entrance, kitchen, bath; a completely livable area?

      Any help would be appreciated