I think mcgrattan summarized the focussing concerns pretty well. I can't speak to the Nikon system specifically, but in general I think it's true that the advantages of RF focussing are greatest in low light and/or for aging eyes (that would be me).

One thing to think about might be a Bessa-R, which should be much cheaper used than the later M-mount versions; it doesn't get you into M lenses, of course, but if cost is a concern you'd probably mainly want screwmount lenses anyway. That might be a way to get a toe into the Bessa ecosystem without having to sell a huge amount of equipment to finance it.

If I remember aright, the Bessa-R and the R*M bodies will still work without a battery---you don't get metering that way, of course, but the shutter works. I get pretty clear warnings when the battery is fading on my -R; the meter LED gets more and more reluctant to go on (but seems still to be accurate when it is on).