The C2 machine is fine, I use it regularly in a nearby studio besides other training and it's perfect for training. If the studio wouldn't be easily available I would buy a C2. And, by the way, my wife too started to be an avid rower after giving the machine a try.

I was rowing on real boats during my school and university days, but sadly never found the time afterwards to get join a club and row in teams.

Rowing machines with a water container are en vogue, but they are heavier (if filled with water) need regular water maintenance and the training effect isn't better.

Edit: here's a good intro to using such a machine: https://www.youtube.com/watch?v=zHHy0KpFKvE