Help with Co-Partner Requesting Monthly rent from a houseHacking Deal.

[Nicholas Gangwer]

Good Afternoon Everybody,

For the past 2 years, I have been managing a property that I found, Financed, and Upkeep. For the past 2 years there has been an open room in the house that was not lived in, However during the school year I moved in for about 7 months.  It's our property and an open room so I didn't think it would be an issue. Plus it was easy for me to work on the property while I stayed there which I finished with the remodel.  The main reason for acquiring this property was for me to save money on rent which is why we got it.

Our agreement: (60/40 spilt of Net profit) (I am paid a PM fee) and an (ROI from my downpayment until the lump some reaches the downpaymeproperty found the property, negotiated, manage, and remodel

-co-partner signed the mortgage because I had no credit 

When We were going to pull out profits my copartner said "that I have to subtract the rent that I didn't have to pay each month when I was there, in his mind it was 600 more in cash for me not having to pay rent and 600 cash we where having to pay?? However the room was empty and in the middle of the school year, no one would sign a lease. We are also co-owner of the house and I got this property for the sole reason of not having to pay rent. #HouseHacking. The rent from the other rooms pays for the mortgage and we pulling good returns without the last room booked...

Is having an open room, not a sunken cost? Therefore no one is (Paying) for the downfall of the empty space, our Net profit is just lower but we are still Positive.

I am not understanding his side of this argument, I would really appreciate someone's help! Thank you SO Much!