Currently residents of single-family neighborhoods can’t rent out extra space they may have in "detached accessory dwelling units", such as an apartment above their garage, although basement apartments are legal.
Granny flats provide a variety of benefits. They increase density, supporting better transit and more services for the neighborhood. They increase the housing supply and create affordable housing in the city. They can give homeowners a source of income to help with the mortgage. And, with kids returning to the nest post-college and aging parents needing more care, they provide extra space with a degree of privacy.
The program would limit the impact on neighbors by requiring one off-street parking space per unit and restricting the size of the new units. Reactions to a demonstration project in Magnolia, in which a wheelchair-bound resident added an apartment for a future live-in nurse, were very positive: 65 percent of surveyed neighbors rated the project "good". While some are worried that allowing rental granny flats will turn neighborhoods into "ghettos," (huh!?) that doesn’t seem to be the case in cities that already allow them, such as Mercer Island, Kirkland, and Redmond.