Worth it? It all depends.
How long has it been idle? Has the membrane dried out?
How long since it has been sanitized?
Assume all the filters need to be replaced unless you know otherwise
Do any orings need to be replaced to fix/resolve housing leaks?
Is there excessive rust?
Does the pressure gauge work?
Does it come with a TDS meter?
Does it come with a housing wrench?
Are the housings cracked/chipped?
BTW... Realize that what that system has is a re-labeled 75 gpd membrane.
I always recommend that if you've never owned an RODI system before, buy a new one. If you've already owned one and paid attention to it re maintenance/repairs, and are very familiar with how it works and what questions to ask, and you are handy, it may be ok to buy used.
Russ