House Hacking Query: Do I factor in my paying rent?

[Ken Alce]

Hi all! I'm brand new to this community and look forward to learning (and, in time, giving) as much as possible! I'm located out of Baltimore, MD. 

When running the numbers on a house hack opportunity, do you factor in how much you'll be "giving" in rent? I'm renting my apt. right now for $1700. I intend to move to a duplex and rent out the other unit. When I run the numbers do I factor in that I'm paying $1700? 

On one hand, I'm trying to take advantage the "live for free" (which presupposes that I'm not paying rent). On the other hand, when I run the numbers, unless I factor in a second rent (i.e., me), the numbers look terrible, leading me to suppose this means it's not a great deal.

What do you think?