I'm looking to add more units to my portfolio and more connections in my network.Leave a comment if you're interested in multifamily investing in Seattle, King or Snohomish County. 

Have the neighbors ever complained to the city/county?

I can get the info from the county tax records but still need to take another step?

You can find a lot of that info in city/county websites and real estate data providers.

If you are looking for cash flow, storage might be great in one area, but one county over they get 0 cash flow.

TLDR: I'm buying out my house from my ex-boyfriend in Seattle (King County), Washington and I'm struggling to find what the REET if I'm buying my ex's stake in the house.

If you look up here in UT county or SLC county I'd love to be a resource for you.

The state of Oregon and the city of Eugene both have complex and unforgiving regulations that most often favor the tenant, so it is important that you learn about these laws so that you can make strategic choices now that avoid pitfalls later.Fortunately,  the Oregon Rental Housing Association at the state level and the Rental Owners Association of Lane county at the local level can provide you with excellent resources. 

For instance, one property seems to have an extra bathroom that is not listed in the county records.I plan to make some modifications, including removing a closet wall to expand a bathroom and taking out a kitchen island that contains electrical outlets and a switch.

After that, I would encourage you to go to your county recorders office / court to request data yourself.