We purchased a Gold's Gym last year and it works for all of us; even my dh who actually runs on it. They have a number of options 450, 550, and 650 all well under $700 if you check around. We went with a Walmart sale just after Christmas (saved almost $200 as it was last year's model) their sale price was worth lugging it home and upstairs ourselves. However....we will never move that thing unless someone else does it.
Ours is upstairs and you can hear anyone walking fast or running in the living room. That's something to consider if sound is a problem.
I don't love it, but it gets a workout during the cold months here by all of us. We would all prefer to walk, run or jog outdoors, but that isn't always an option here.