I used RO water for a few years and it's great, but there are drawbacks. You can find basic to inline systems all over. I have good or decent town water. But.... RO water is big for a new grower because it reduces, almost eliminates any problems that are water related. You're basically dealing with pure water. And being a new grower, it's one less thing to worry about. Not necessary, but very helpful. The drawback is there's waste water. Can be a good amount also. Especially when yer flowering 20+ 7g plants,,, So, you have to manage the waste water, and pay for it.
I've since switched to a water filter called
boogie blue, it's a hose end carbon filter. It's much cheaper and for a person with good, town water, it works for me. Plus, I don't flower 20 plus plants anymore... at home.