I am surprised it has not been mentioned. Even though it is no longer made, it is still available new and it is a worthy companion to my 16 year-old M6. The only significant differences are the viewfinder (the Ikon's is slightly better), the electronic shutter on the ZM is more accurate (but I prefer the Leica's quiet mechanical shutter) and film loading is a little easier with the ZM.
Before jumping in and spending a lot of money on a new camera and lens, you should try someting on the less-expensive side. There are literally hundreds of kind of fixed-lens rangefinder cameras, and some are stellar performers. .
Along those lines, you couldn't go too far wrong with a Konica--A Konica III or Auto S2 can be had very cheap. They're fixed lens, but the Konica Hexanon is awesome.