Just registered on this site today, still need to update my info but I live in the Seattle area. I'm rather visually disabled and have some other health problems and some machines/frames do have issues you should be aware of.
The machine I use is set for my tall friend who uses it and is several inches too high for me to stand comfortably, but I make do. Because of my visual impairments I often have to make paper designs on parchment paper so I can see what I want to do -- wish I was better at coming up with ideas/freehanding but so far I can only do a few types of stipples free hand (stars, hearts, flowers...) for more complicated designs I use the paper.
One of my friends has a machine that is set for her to use while sitting, along with a floor mat and a wheeled chair. Her set-up uses a frame with her existing machine.
There are often some really good deals on Craig's List but you have to wait/look for them and be prepared with cash. The Sew Expo at the Puyallup Fair Grounds in the Spring is a great place to see current machines.
Longarm U as already suggested is a great resource.
I really do recommend a stitch regulator and if you can afford it a computerized/tablet machine. My friend that bought the system I use found it wasn't quite as easy as she had hoped (it does have built in stitch regulator) and that loading the quilts is still a bit physical but that gets better with practice.