It is a statewide rule that you cannot use an ADU for STR.

Here in Columbus, we're still seeing deals here that hit the 1% rule with positive cash flow and lots of potential for appreciation.

There are rules to follow!

Not following the requirements (within Seattle city limits will likely have additional rules and regulations) opens the seller up to liability.Additionally, the seller always has the option of offering "cash for keys" arrangement but be sure that no funds change hands until after the property is vacated and locks are changed.John

There are rules and exceptions to the rules -- it's actually pretty interesting if you take the time to research it.

Has anyone also finished a project since the new rules came to place but placed a tenant meanwhile before they had these?

And I’ve bought 4 or 5 houses from 0% interest for a year credit card loans so don’t rule out those offers to combine with your 80k to buy something.

As a general rule of thumb it's smart to pay for 10 - 20% of the total costs (purchase price + rehab) out of your pocket and then finance the rest with hard money. 

You should talk with one that understands real estate rules and another that understands special needs trust and SSI rules. 

As a general rule, each entity that files a separate tax return (partnership, s-corp, c-corp, etc) will need its own QBO subscription.