500 bucks and you can't hardly go wrong, unless there's rust in the wrong places.

Check the points where the suspension mount to the unibody. Called subframe mounts in MB-speak, wishbone mounts to the old-timers. Also check the jack points (pipe stubs with the holes pointing out the sides of the car). Jacking points can sometimes be repaired but repairs to those subframe mounts are for the experts only.

The other common place for rust is the front fenders behind the headlight trim, but that's fixable.

Otherwise it's a great car to learn to diesel and to learn the quirks of independent suspension. At this age I wouldn't make it my primary car until you're completely comfortable about repairing it. Most of the time you'll be the only one on the road who knows what's going on.

__________________
daBenz - 1970 220D