is the actual wellhead location relatively adjacent to your land, by chance? if yes, certainly I'd pursue a deal. if not and you're buying via (easements), little to gain? (on a small system- didn't mention the number of hookups but I'm guessing 2-3 or certainly less than 10?)
talk to the dept of health first (records requirements etc), establish what upgrades/maintenance required, line up a reliable repair/handyman/type person, consult lawyer, and then make your offer, see if you can buy the land it's on via lot line adjustment (ideal scenario).
a lot to be aware of, such as system upgrades or county code changes bringing in the requirement to add metered connections to an older small system, for just one example.
Otherwise- owner doesn't want to manage, I doubt you really do either but could be wrong. Maybe you can convince everyone involved to convert to a community owned system,
with a shared maintenance agreement, reserve funds,
Just need to find the smoothest path forward to needed upgrades like an above ground cistern, pumps, backup generator, better filters, or whatever to make the system function 100% of the time
$1500 is minimal, spend it if that's the way forward. Pay for the materials and hire the labor yourself if needed/possible? I'm sure there is a compromise easily in there somewhere where you can pay a licensed business to do the work and receive an invoice for your $1500/etc. The least I've seen spent on a new shallow well (recently) 18-20k, of course that's regional but still. .