Over lunch the other day one of my audio pals mentioned cassette decks are going for next to nothing on eBay. "Really?" I said. "That sounds like something I should check into." He was more right than I imagined.
The first thing I noticed was prices were dirt-cheap, lots of choices for under $50, £50, AU$50, and most were dual-well (double), auto-reverse cassette decks that deliver hours of uninterrupted play time. They were hugely popular back in the day.
As I continued perusing the listings I stumbled upon high-end decks from the likes of Denon, Nakamichi and Marantz going for under $100! Regardless of manufacturer, the best decks are always single-well decks, with three tape "heads" (erase, record, playback), and two or three drive motors. Lower-end models make do with two heads (erase, record/playback) and one drive motor per well.
Buying used vintage gear is not without risk; the deck might not work properly, so proceed with caution. Ask the seller questions, has the deck actually been listened to; just turning on and lighting up, or seeing the cassette tape moving doesn't mean it works well enough to listen to.
If you're buying the deck in person, bring a well-recorded tape with you to listen to. Check all transport functions -- play/pause, fast forward/reverse, stop, etc. -- and make sure they all work smoothly. Turn the Dolby noise reduction on and off to confirm it works. Also listen for wow and flutter (unsteady sound), distortion, or if the sound is dull or muffled. See if the dealer/owner will let you try the deck at home. If it's a dealer, ask if they provide a warranty for repairs. Of course, dealers that provide those services charge more, but if you can buy with assurance you won't get stuck with a poorly performing deck, so paying extra might be worth it.
There's something going on with cassettes in 2015; I definitely didn't see that coming.