Like the idea Chance, but you might look for a properly zoned, up to code, duplex with a separate units (entrances, meters, addresses, etc) just to get a clean start. 

There are between 5-6 that serve the area I plan on being in but there are some serious red flags.

I am really stepping out of my comfort zone this year not only with investing but also even posting this post!!

The property is zoned for residential two family unit.Thanks in advance.

In my opinion, with Seattle's red hot market and escalating prices, the only places you'll find a deal, is probably in areas you won't want to live.  

After rehabbing costs (you will be inspected by a HUD inspector, and have to meet minimum living standards, which are not that minimum), assuming a 10% vacancy rate (not really a vacancy rate, but more like a "tenant not paying full rent" rate), plus associated costs, my CAP was in the red. 

The land is zoned for the building of 21 units (the project was approved by the city).

We can do ADU's here, but in most zoning categories they can not be split through the planning dept and sold separately.  

Check with zoning and confirm you are legally allowed to rent out the property.  

LIFE-CHANGING ACTIONS here.STEP 1-20.You need to get you personal home rent-ready... not overboard updating, just rentable... clean and painted etc.Fix any leak faucets, loose doorknobs etc NOW, so that when your PERFECT tenant moves in, they won't be calling you to fix those.Put in new 5 Year Lithium Battery (write the date installed ON THE OUTER SHELL) of SMOKE DETECTORS (draw faint red stripes across the front outer shell of smoke detectors-- red means fire or smoke-- when the smoke clears (if the house didn't burn down) it's ok to reset the smoke detector and finish cooking dinner.ON CO DETECTORS (draw faint gray stripes across the front outer shell of a CO--teach your tenant the gray stripes mean DEATH-- if that alarm EVER starts beeping, they are to immediately raise windows , open doors and call you---even if its 2am--- A REPAIR MUST BE MADE or people can DIE-- little children and elderly go first