Gross Rent Multiplier for Harlem, NY

[Martin Sterling]

Good Afternoon,

Does anyone know the gross rent multiplier for a building in Harlem, NY? Is there a specific place to find this number for various areas?

I was looking up a GRM for Harlem, NY and I found one that said 10. That makes no sense. I have a 4 unit under contract for the very competitive deal price of $1.8M. Currently it sees $7,850/mo in Gross rent, but if they were pushed to market rents, it would be $9996. It's zoned as R-7. 3 more units would give me a gross rent of $17,188/mo. with a GRM factor of 10, that new 7 unit is only worth $2.1M. 75% increase in units and raising all rents 22% can't only result in a 20% increase in value. So obviously, I'm wrong here somehow. Does anyone have some insight?

Thanks in Advance