I have a Concept II rower that I was lucky enough to buy for a relative song.
I would say that rowing is very complimentary to cycling and is a much more rounded workout.
Getting one 2nd hand would be a good idea as these things are pretty bomb proof although it might be worth avoiding those that have had several years abuse in a public gym. They are expensive but as already been said the resale value is high so if its not for you then you won’t end up too much out of pocket.
To keep the interest up there are a number of training plans on the C2 website and improving your times can get quite addictive.
And has already been said learning how to row properly will make quite a difference to your times, also you will need to learn about the drag factor ( no this is not something with Simon Cowell and a load of blokes in dresses). The C2 website will have all you need, plus there are plenty of you tube vids for the perfect stroke.