While I agree there is no learning curve using the camera, it's still useful knowing how RFs work though. There are plenty of options, do you want film or digital ? Are you on a budget ? What kind of photography do you do ?
CV has a very nice affordable lineup of film RFs, and some vintage Leicas are more affordable than one thinks. Epson has its new digital RF and the M8/M9 are selling like hot cakes, although I can't really recommend the M8, at least the M8.2.
What focal lengths do you use most often ? Check viewfinder magnifications to avoid surprises.
I strongly recommend trying them out in a store first, no matter how many reviews you read and opinions people give you, nothing beats a hands on experience.