I live in a condo (40ish yo) and recently a neighbor in an adjacent building had a leak and the board suggested that everyone have a plumber come inspect their units. I just inspected and found various levels of corrosion at most joints with the included photo the worst looking of the bunch.
How concerning does this appear?
Corrosion on copper pipes is a pretty typical thing. It’s a little more concerning if it’s only around the joints. Without cutting a cross section to see if it is actually pitting however its hard to tell if replacement is totally necessary.