Any old aluminum airplane is subject to corrosion, and the full range of airframes from pristine to rotted-out hulks are out there.
The flat spring steel main gear legs also have a corrosion problem. Cessna has issued SBs and SIDs on it, addressing the need to blend out damage and measure the remaining thickness to determine if it's salvageable and if it needs re-heat treating and shot peening. Corrosion pits represent stress risers that can lead to sudden gear breakage. The area under the entry step is a particularly bad spot. Those legs are rare and expensive.
The aluminum castings that hold that leg in the fuselage are also subject to corrosion and breakage.
The small Continentals are famous for leaking oil from the pushrod tubes. The rubber collars at the inboard ends age and crack and sometimes slip off, and there's no solution besides pulling the cylinders off and fixing it. The tubes are swaged into the head at the outboard ends, and mishandling those cylinders when they're off the engine can loosen the tubes, leading to more difficult-to-stop oil leaks. Aging of the cylinder base seals also lets oil out, but that isn't limited to small Continentals.
Get a GOOD prebuy.