Check Ebay for parts availability. Bikes in that range can actually no longer have parts for repairs, a major problem unless there's an online community with parts bikes available.
Presuming it hasn't run in a while, I'd guess the gas tank is rusted and may or may not have a leak. The carbs will have to be cleaned, probably, and the fuel filter changed. Oil and filter change. Brake and clutch fluid changes and cable lubrications. Not sure about how the wheel or swingarm bearings might have survived, but I doubt my '84 has ever had them repacked, so perhaps a non-issue. Check out tires and have some idea what those will cost, presuming their size is still available.
As was just noted in another thread, look for dents in the frame or misalignment in teh subframe.
That's off the top of my head.
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When you're in a car, you're watching a movie; when you're on a bike, you're in the movie. --Robert Pirsig
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