What percentage of monthly expenses should be covered?

[Jack Sullivan]

Hi, I'm looking to purchase my first house hack in the next few months and am working on my system to analyze cash flow for properties. I'm looking to do a duplex traditional house hack, living in one unit and renting the other. When analyzing properties, I'm finding that the monthly cash flow is often negative, which obviously sounds bad but doesn't account for my living for free in the other unit. Is there any rule of thumb or guideline to figure out how much of the remaining monthly expenses I should be covering? Would it make sense to perform the analysis as if I was another tenant and paying market-value rent for the unit I live in? Or maybe analyze each unit separately somehow? Any advice or directions to look into would be appreciated.