Where To Buy A Classic Leica?
If you really want to make like Henri Cartier-Bresson or Alfred Eisenstaedt (whom I once observed running down Sixth Ave in New York loading his screwmount Leica!) you'd better make sure your IIIa, IIIc, or IIIf is in sound operating condition before you buy it. Remember, we're talking about cameras that are 50-70 years old! It's a great incentive for buying your classic Leica in a well-established camera store with a reputation for integrity. That way you can inspect it in person, talk to a human being, and return it (after a suitable trial period) if you're not satisfied. Based on cruising the Leica rangefinder section of eBay for about a week, I'd say that your likelihood of getting a great deal from a private seller is not any better than it is at a store, and the risk is considerably higher. In the first place, there are many important things you can't tell about a camera by looking at pictures of it. The forthright descriptions of honest sellers are more helpful, but bear in mind that eBay's anti-fraud enforcement powers are strictly limited. That having been said, there are many reputable stores that sell on eBay and those with excellent feedback records who offer return privileges may be worth a shot if you see what you want at a good price.

Which Model Is For You?
With any camera in this age bracket, condition is everything. In general, Leicas in cleaner cosmetic condition will hold their value better, and models in perfect operating condition are less likely to require repairs. Personally, I've always had a special affection for the Leica IIIf red dial (the flash sync dial under the tip shutter dial has numerals in red) with built-in self-timer. It looks really cool and is the last of the real classic screwmount Leicas. However, the nearly identical black-dial IIIf without self-timer is just as good and less expensive--a cohort of mine recently bought an E++ one for $250 with a decent (G-VG) 50mm f/2 Summitar lens. If you don't need flash sync, clean Leica IIIc bodies and IIIa bodies with excellent shutters and rangefinders are readily available at $200-$250. I myself just bought a Leica IIIc-to-IIIf factory conversion with self-timer and sharkskin covering (a plus) with coated 50mm f/3.5 Elmar for $300, including a nice original case and lens cap. My buddies at the Leica Historical Society of America assure me this is a steal.

If you want to go whole-hog on the Leica screwmount kick and have a few hundred extra dollars to spend, go for a IIIg, which is about 1¼4" taller than the aforementioned classics, but has a bigger, brighter viewfinder with parallax-compensating frame lines for 50mm and 90mm lenses--and that cool built-in self-timer. Clean-but-not-mint IIIg bodies currently fetch about $650-$850 (a few hundred less than five years ago), and I just missed a really nice one with E- 50mm f/2.8 collapsible Elmar lens that went for just over $1000.

Which Lenses Are Best--And Affordable?
As for lenses, you're better off with coated ones (and a lens hood) if you want to take sharp, contrasty, flare-free pictures, but the uncoated 50mm Elmar will do quite nicely for general picture taking. Coated 50mm f/2 Summitars are excellent all-around picture takers--not stellar wide-open but good at f/2.8 and excellent at f/4 on down. Uncoated 50mm f/2 Summars are the perfect match for your IIIa. They're pretty soft at f/2 and f/2.8 but have nice bokeh, take lovely pictures, and are pretty sharp at smaller apertures. The late 50mm f/3.5 Elmar with red depth of field scale and f/22 minimum aperture is more expensive than the earlier versions and is said to be a tad sharper. The 50mm f/2.8 Elmar is very good, but expensive at about $300-$350. My favorite lens is the 50mm f/2 collapsible Summicron, a superb lens that's notorious for its soft coating. However, if you'll settle for one with a few minor scratches and cleaning marks, it's yours for $350-$450. Yes, the 35mm Summarons, 90mm Elmars and Elmarits are also very nice, but that's a topic for another day.

Take Me To Your Leader!
Oh yeah, one final thing. Once you get your new-old Leica home, have stopped salivating over it and decided to run some film through it, make sure to cut the film leader with a 4" tongue corresponding with the little diagram emblazoned inside the base plate. If you don't do this modern short-leader film will not take up properly. Hint: You can trim the leader by eye with a little mustache or eyebrow scissors, but don't cut through the final sprocket holes closest to the cartridge or you can cause problems. Leica used to sell a gorgeous satin chrome-finished film-cutting template and a little knife for this purpose, but both are long gone. Sure, you can probably buy both of these vintage Leitz logo items on eBay, but they'll probably set you back half the price of a IIIc body!