How do I make an educated guess at the appraised value of a 6-unit?

[Michael Wentzel]

Hey friends,

I own 7 residential rental properties with 1-4 units. I'm under-contract on three more of this type. But I am also looking at my first 6-unit. I have talked to the Realtor, the owner, my contractor, my property manager and my partner. It looks promising. 

But I'm not sure how much to offer as I am not sure how to make an educated guess of where the actual appraisal would come in at. I know residential appraisals are built on comparable sales. But how do you identify the value of a small apartment block that would be considered commercial (over 4 units).

Mike