Cheap can be dangerous with an acoustic 12-string! Lotta structural tension from those strings. As far as new, I'd feel fairly safe with a Seagull S-12 (under $600 at MF) like this one:


One of the nicest 12-string acoustics that I've ever played at any price was a Larrivee a few years ago. It was around $1200, if I recall correctly. Sweet! Guilds rock, too.
My brother has an old Italian-made EKO copy of a Gibson that's surprisingly playable AND toneful. One quirk: the string spacing is normal at the nut, but at the bridge all of the strings are equally distant from each other. As in not doubled like up at the nut. Still, it plays great. Go figure! (He's been threatening to sell it, let me know if you want me to get a price from him).
Cheers, Tim