I love the old Macintosh stuff. I never owned a compact mac but when I got one recently and decided to try programming I wanted to do it the way they did it back then using the hardware and whatever ran well on my SE/30 (which at first was System 6 but the textbook that the study group on TinkerDifferent was using was written for 7 so i switched!). No internet needed (and I’m not (un?)lucky enough to own any networking hw for it. Just transfered the files out using floppies or my SCSI to SD device)

You can connect System 6 using MacTCP.

I’m not a fan of System 7 particularly, but I find that 8.0 up through 9.1 make nice “zen mode” operating systems. They have reasonably modern touches like sticky menus (don’t need to hold down mouse button to keep menu open) but are so much more “quiet” than modern operating systems. System 7.5 isn’t too bad and I actually used it back when it was current, but my interest in old macs skews more toward 1997 onward, most of which boot 8.0 or newer.

Earlier OS X releases are decent at this too. I find 10.2-10.6 pretty cozy.

What mac would you recommend for a nice home setup to run os9ish and do things with it (e.g., writing)?

I think AGP or Quicksilver G4s are nice for that use case. They have lots of ports and stuff for expansion, their RAM is easier to get than pre-G3 EDO DIMMs, they can have decent GPUs. I would avoid MDDs, they run very hot and have very noisy fans.

I have a soft spot for the 9600, which can take PCI cards for things like USB or SATA, but their RAM modules are hard to get and their CPUs are very slow. I would also avoid anything older than that, except if you really like the hardware. It’s very difficult to find NuBus expansion cards.

Agree with the sibling comment, though if expandability isn’t as desired or you don’t have the space, G3/G4 PowerBooks and iBooks may be a consideration.

I’d personally say look at models with at least a 400Mhz CPU — PowerBook G3 “Pismo” (I have one of these) or any of the white iBook G3s/G4s (though I’ve heard the keyboards on some of these develop a funky smell with age, which I haven’t verified personally). A Titanium PowerBook G4 may be an option, and they’re historically notable because they basically defined what modern laptops have looked like ever since, but you’ll probably need to do some repair work due to the various issues it’s known for (like hinges that break with time).

iMac G4s are super cool but make sure that the one you’re looking at is one of the models that natively boots OS 9 (some only boot OS X) and that the spring in its screen arm is still in good condition (some have been known to droop with time).