I have written about rowing on Concept2Rowing machine on quite a few occasions. The choice of machine was quite simple-that was the one at the gym. I was aware however that it was one of the popular types of rowing machine.
Today I found an interesting article on Coach Magazine where they have reviewed the various types. And most importantly they list the typical prices when new. I have often looked at eBay for a machine and been uncertain whether the price was a reasonable one.
Any way, here is the link to the article https://www.coachmag.co.uk/gear/rowing-machines
Also whilst browsing the net for estimates of the calories used whilst rowing, I came across the following. https://www.rowingmachineking.com/
Again the site seems to offer a full review and helps one decide which machine to choose
One thing that has motivated me with the Concept 2 is their on line logbook, so that you can record the distances that you have covered. There is also a worldwide ranking, fortunately this list is arranged by age bands as there are some serious athletes see. https://log.concept2.com/
If you are really getting into the sport then there are also indoor rowing championships to follow or compete. https://www.concept2.co.uk/indoor-rowers/racing/calendar
There are even world championships to be held in Paris in 2020 https://www.concept2.co.uk/indoor-rowers/racing/wric
Anyway I hope that you are still making progress. With a rowing machine one of the nice features is that at the end of any session or when you’ve had enough you are still sitting where you started.