My advice would be to ask yourself why you want an interchangeable lens rangefinder. I’m not saying you shouldn’t want one, but camera lust often begins with an idea of what you could do if only you had something different… What does it offer that you don’t have now? Compactness? Quiet operation? Ease of use? Uninterrupted viewing? More or less so than what you already have?
If your question wasn’t specifically about interchangeable lens rangefinders I’d suggest picking up the first decent Spotmatic or Nikon SLR to come your way and call it good. If money is a concern you’ll be money ahead no matter which way you look at it.
After considering what it is you really want, and finding that it is indeed a rangefinder, I would then save up and get a Leica. Rangefinder lust… it begins and ends with Leica, unfortunately. Either LTM or M depending on your preference. The M bodies are very slick to use, the LTM bodies less so but still very capable.
I disagree that the camera body is irrelevant. Ever used an interchangeable lens Voigtlander Prominent? Talk about great lenses made almost useless by a clumsy-borderline-infuriating body and viewfinder. Sure you can take great pictures with it. You can also miss a lot of great pictures with it. Perhaps an extreme example, but it proves the point that ergonomics absolutely do matter.
The M cameras just get out of the way and do their job, plus you can use a huge range of lenses, from $15 Industar-61’s to vintage Leica, Canon, Nikkor, etc. to the best modern designs.
Nothing in particular against other options. I wouldn’t turn down a decent Canon if it was working well. Nikons are great too, though lens choices are limited. But Leicas offer something quite valuable in return for the price: a very high probability they will remain serviceable for many decades to come. The same may be true for some other brands, perhaps to a lesser extent due to quantity and demand. Leica made a whole lot of cameras and there is still a strong demand to keep them working.
Sorry, I don’t mean to evangelize, that’s not the point.
I was in your shoes 2 years ago and ultimately saved up and bought a nice M3. It was worth it. I like using it. I don’t care if there is a bandwagon full of Leica-owning dentists, lawyers, engineers, film hipsters and YouTubers. There is still room on the bandwagon for normal people who just want a nice camera.