I am selling my Concept2 Rowing machine (no space to use it now, with new baby). It's in excellent condition; it is perhaps four years old and I have maintained it carefully.
Concept2 is a gym-quality rowing machine; it's very highly rated and incredibly durable. It's got a ton of features (including a tracker that can sync up with your phone or display on an LCD screen), variable difficulty, and it easily comes apart into two pieces for storage, and has wheels to enable it to be moved easily.
At the time I bought it, my model was called a "Model D"; they've rebranded slightly, but this is almost identical: https://www.concept2.com/ergs/rowerg
A new one is about 1k, plus about 100 in shipping, which can take up to a month.