Here's a Dahon folder I bought for $25.00 and it cleaned up well. Didn't keep it long since I found it slow even with the huge chain ring and the steering was twitchy. The 16 inch wheels forced you to be constantly looking for pot holes or large cracks.
The orange single speed was converted from a used Walmart road bike I picked up cheap. The aluminum frame was well made but everything else on the bike attracted magnets. The burnt orange color is a rattle can engine enamel. I got the bike down to 23 pounds but it felt unrefined and cheap. If I upgraded all of the bearings it would probably feel better but I just sold it and made a few bucks.