You might try a Leica Barnack screwmount (iiic or iiif) to start with if your vision can handle the squinty viewfinder. They are cheaper ($600-800 with lens) than the M series, yet can take great photos. All the ones I've had needed CLAs, but then worked like charms. Try to get as new as possible (late 50's). The iiig is the best of the screwmount Leicas, if you can afford it (about $1K with lens); nice larger viewfinder. I got an early M3 and have had a lot of problems with it, like the counter not working, and my CLA person unable to fix it; again, look for as new as possible/avoid the early numbers.
Best of luck; there are a lot of these available! Careful, they can get addictive.