from a quick glance, these machines are plumb only, now id presume the seller who can afford such a machine will have sorted water,
id be looking at how easy it is to plumb in your home, as well as the associated filters and water conditioners, next up would be the up keep of the machine, is there some one local to service it should it need it,
the machine itself will be fine as they are a high class machine,
id say in terms of an investment a machine like that will hold some if not all its value, come resale time, how ever finding some one who wants to spend that cash on a machine of the age may be hard to sit on, but its end game and in theory you should never nee to replace it,
i say do it, you only live once, but only if you can afford it,
me id be buying this in a heartbeat
its a bargain and we know the seller too.