Welcome to Tiny Homes, an idea that is more popular with minimalists than with neighborhood associations and zoning boards. We'll point out the fun parts. You'll have to check out the logistics and legalities - but this one has been in place since 1947.
There are still tiny houses in Seattle that aren't ADUs or DADUs. When they were built they had names, like 'cottage'. Where's the romance in an acronym? Of course, where's the romance in any house? You bring it to it. Here's a 1947 cottage in Delridge with an asking price of $289,000. That gets a 2 bedroom, 1 bath, 672 square foot house. Not too tiny by the standards of post-WWII, but tiny today - unless you compare it to apodments and tiny houses on wheels. This one even comes with 4,968 square feet of fenced flat land; which makes gardening or dog runs easier. One advantage of owning a house, you get to decide whether pets are allowed. The current residents includes a photo-bombing cat. Let that lingering heritage confuse whatever pet moves in with you. The details of the interior may have less to do with the sale than the neighbors. Next door is a gas station; but walk a few blocks west and find Camp Long and the West Seattle Golf Club. Buy a small house and maybe have enough left over for greens fees.