Avarage cost to build a 20 unit Apartment? Seattle area

[Simon Hatzey]

Hello My names is Simon and I am a real estate broker/investor.  I am new to this form.  I live North of Seattle and I am hoping to get more info on how much it cost to build  4-story, 20-25 unit apartment(Avg per sqft) .  We have a land in prime Shoreline area.  The original plan was to build 5-townhomes and sell but we are considering building apartment and hold long term.  Any feedback greatly appreciated.  

Thank you,

Simon