have a look at either the flashforge adventurer 3 or monoprice voxel (exactly same machine).
The monoprice rebadged is cheaper, under $400.
While the flashforge has some extra software and links to an online file service.

It's about as close to a plug-n-play as you can get and the flashforge service is either very good or atrocious, depending on the review in question.

As far as renting a lower end printer - not seen anything round here. You can rent the 3dp machines and the super expensive multimaterial machines. But for the multi-jets you're looking at thousands a month plus materials.

Basic 3d printers aren't difficult to maintain, service contracts are generally a waste of money.

Your best bet is to get a cheap machine around $500, and show them what it can do.
Once you've convinced them start looking at machines like the leapfrog bolt: https://www.lpfrg.com/products/leapfrog-bolt-pro/
One of the best sub $10,000 printers I've yet seen.
Or just get a bunch of small cheap printers :-)

Buying a sub $500 for proof-of-concept just makes more sense than spensing alot more on renting something that probably won't be much better, from a results point of view.