Estimating Expenses for House Hacking

[Jason Porto]

Currently I'm analyzing numerous potential multi-family properties (duplex, triplex, 4-plex) and want to make sure I'm estimating my expenses correctly. The only reason I'm looking at multi-family is so I can house-hack and live in one of the units, which means that I will have one fewer unit to collect rent from. Since most of the expense estimates are derived as a percentage of the monthly income, I'm curious how others handle this. Do you A) consider the potential monthly rent that would be collected should all units be rented, or B) cut yourself out of the equation and only count on actual rent that you will be receiving from the other units? Am I overestimating in the first scenario, or underestimating in the second? Personally, the first scenario makes more sense to me since I am still living there are making use of the space which will cause things to degrade or break and need upkeep and repair. But, let me know your thoughts.