It's a lot cheaper in to do this in the US and with a long term view, my total outlay was under $3000 for a z800, z114, ds6800 all in with transportation. I also temporarily had two DS8870s but resold them because they were worth a lot more than I paid and I will pick up another for cheaper over the course of this year. Both of my frames have HMCs, the z114 was even IBM banded and "MSQ" maintenance service qualified which means they'd come and set it back up for some not-too-outrageous monthly fee if it were in production use.

The z800/z890 are probably optimal for hobby use even though they are old because they have modest power requirements and are relatively light and not too wide like the z114 which is absolutely massive.

Actually a P/390 (MCA or PCI card), or Multiprise 3000 (deskside hybrid CMOS/PC server thing) would be even easier but those are very very old 31-bit systems at this point. (I also have a R/390 setup and can comment on that if desired)

Now that said, this requires A LOT of dedication to get right. You need to understand at minimum shipping/transport issues, as well as electrical requirements and installation (or be willing to consult someone that can advise you on phase and conversion if necessary).

After that, you definitely need an HMC (a PC used to do things like load the OS) or at least a recovery disk and a lot of patience to set that up in emulation or on other hardware.

And then, you need a FICON (or older ESCON) capable array. Connor Krukosky goes into detail about what it's like without that, and you are extremely limited (basically Linux) in what you can do without FICON. A ds6800 is the easiest way to do that because it is a small rackmount unit, but they are also in demand for that reason. DS8ks are quite cheap all things considered, but serious iron like the frame itself.

And then finally you need some OS media which is also non-trivial to get (although there is or was some "out there" on file sharing).

I am willing to help anyone interested in this kind of thing for fun and preservation of incredible technology and history.