If you're really looking at a classic, you're probably not going to be able to be too picky if you want to buy local (and I can't imagine buying a 40+ year old car without seeing it in person). Just keep searching CL for cars in your price range until you see something you like - looking specifically for a late 60s Electra, for example, might take a while to find a match. Something like that should go pretty cheap though, convertibles are more than sedans but should still be well under $10K. My parents, for example, had a 1970 Cadillac Fleetwood sedan 7.0 that was in outstanding condition that was worth like $3K or $4K.
As for Jeeps - they haven't changed too much until the last 15 years or so, so as far as the older generations they're pretty similar. My friend had a '74 CJ5 that didn't look a ton different than one from the late 90s, so "how old should I be looking for" isn't really the question, just find one in good shape and you should be fine. Repairs are fairly simple, another friend really didn't know much about cars before he got his Jeep and did major engine and transmission work himself before it was all said and done.
