You might consider a Mercier Nano, which doesn't fold but has easily pulled wheels and a short wheelbase, and should fit in a trunk or apartment fairly easily. There is a long lasting post about them right here in Bikeforums folding. Sturdy and not expensive. I have a Brompton and Xootr Swift, and it isn't as nice but not that far away either. It seems most folders fail at the hinge but that's not a concern with this bike..