Looks like it has been neglected, but that's reflected in the price you were offered it at. Very rare find and clearly needs a tidy up. If it runs well in that condition, I would think a good service and a clean up would get you going. If you can knock a bit off the price because of the cosmetics, it would pay for some paint. It may be worth looking at a price for a new trim and tilt motor cover and seal if you were keeping it. If not, as long as the corrosion is not too bad, you would get your enjoyment out of it. You must check the shock mounts though as most outboards are a pig to get apart after a few years. Simply turn engine fully to one side and take hold of the front and rear of the tray, try to push it further than the steering travel in both directions, it should be firm with only slight movement, if it is slack and there is lots of movement, the mounts are shot and you are heading for a large bill.