My printer is a 6 year old Roland. It's the same as the new ones maintenance wise. Routine cleaning and replace consumables is all I've ever done. Swab around the heads, swab the wipers, put a little cleaning fluid in the cap tops and you're good to go. Wipers a couple times a year. Dampers and cap tops get replaced when they go bad. That's about it.
HP latex pretty much take care of themselves from what I understand. You get a notification that something needs replacing and you do it. Print heads are consumables which can be good or bad depending how you look at it.
Unless you get a lemon they are all pretty good. If you hang out here long enough all kinds of used equipment pops up.
One thing I forgot to mention. You may want to just do the design and sub out the rest. If I was starting over that's the way I'd approach it. Sometimes the "shine" wears off mighty quick then you're stuck trying to unload equipment.
Our printer only gets used for small size, short run, tight deadline jobs. Bulk orders, large pieces, huge banners etc...get subbed out. I realized many years ago that trying to keep everything in house trying to maximize cash flow was actually doing the opposite.
Leverage market expertise and equipment. Nothing more satisfying than designing a job then letting someone else suffer with making a thousand perfect copies. Take that to the bank.