House Hacking when your partner lives there and you dont

[Spencer Joseph]

My brother and I want to buy a 2 family house so that he can live in one side and we rent out the other. Because it is his first time buying a house the plan was to put down between 3-10% (which we would evenly split). The area we live in is fairly expensive and most multifamily homes are around 600k. Because of this the rent on the other unit does not cover the cost of the entire mortgage (about $1,600 short). 

With that being said who picks up the remainder of the mortgage? Do I split that additional $1,600 that is left over with my brother (thus taking a huge loss, -$800 a month)? Does he absorb the $1,600 as rent? I cant imagine that every house hack covers the mortgage entirely so I am trying to find out when it becomes worthwhile or a "deal". 

How do we make it work being that he will be living there and I will not. How do we make it fair so that we are both getting something out of this. 

Thank you,

Spencer