I haven't lived in Seattle, but I've visited a few times, and the most recent time I rode a borrowed bike there. You can get many places by bike. I suggest you try that and rent a car whenever you need one. After a year, add up the money you've spent on rentals and see if buying a car would be justified. Chances are, it won't be.

There are some serious hills there, but you may do OK on them anyway.