I picked up a Dahon Helios this weekend for AU$150. It is almost brand new. It is the same as the 2006 Helios P8 but mudguards and carrier rack is part of the package.
The owner had a crash with it and the front wheel was slightly out of true; he also thought the forks were bent. We discussed it and I told him the bike looked just fine to me in photos he sent; however he'd already started selling some of the parts, the derailer hanger and the chainring specifically. I told him I'd take the whole lot and we agreed to the $150. He was able to get the hanger and chainwheel back from the other party who'd not used them, so the bike ended up complete, albeit with slightly wobbly wheel and potentially bent forks.
So I got it, trued the wheel (5 minutes), adjusted the cone nuts which were knocking, did the front brakes and started on the fork. But I could not detect any misalignment in the fork at all, even though the handlepost did angle off to one side. It turned out the handlepost was rotated slightly, giving the impression of going off to one side. Quick fix there, and now it is 100%!
It had not done even 500km, the back cogs are still almost free of chain grease, clean as new. The brakes and rims are just about spotless.
Took it for an hour ride yesterday. I won't be keeping it. The handlepost is unbelievably flexy. If this is Dahon's much-touted immensely stiff handlepost then I don't know what their definition of stiff is. I can twist the whole bike through a torsion movement such that I get more than an inch of side-to-side movement at the bars! In contrast, my R20 is much stiffer, I get a few mm, while the Swift gives a new definition to stiffness. My wife's Dahon Yeah with almost identical frame is also better, it has the cheaper steel post which is ironically superior in several aspects.
The SDG saddle was OK, but at the end of an hour my butt was getting warm - signs of lack of blood flow. More standing up is required, but with that flexy post, not such a great idea. Still, one of the better saddles I have tried.