Cost to Convert 400 sq. ft. Detached Garage to ADU in Portland

[Andrew Tupper]

Hi Everyone,

I am a new investor potentially looking at my first deal. I am trying to figure out how much it might cost to convert a detached garage into an ADU in the greater Portland, OR/Vancouver, WA metro area. The garage already has electricity and is currently serving as a shop/office with at least one dividing wall between the two. It has a cement floor, and multiple windows. It sits about 15 ft away from the main house at the end of the driveway and is about 400 sqft. My thought would be to add a small bathroom/shower and kitchenette and make it a 1 bedroom or studio-type layout.

The idea would be to live in the main part of the house owner-occupied and convert and then rent out the garage/ADU for extra income and then move out in a couple of years someplace else and rend both units out.

Any thoughts/suggestions would be greatly appreciated!