Rear control arm mount rust on w124 common?

[jake12tech]

I've found structural rust on my w124 that is pretty bad that I won't drive the car over 65 and I avoid potholes. It isn't my daily driver anyway with its many issues (mostly deferred maintenance, drive the hell out of it and turn the radio up). Has anyone else experienced this? The car looks like its been driven in salt and never cleaned or spent its time down by the beach. I'm going to fix it, but its way out of my league being its structural repair not like a rocker rot or something else. I'm sure it'll be about a 1k or 1500 alone for the repair.