As long as the hull is in good shape and the price is right, go for it.
Most tin boats used in freshwater have a very long lifespan as long as it is not damaged/really abused. An '80/81 has a lot of life left in it.
Check it for leaks, look for obvious damage and see if the wood decks (it is has wood decks?) are still strong.
Be prepared to replace carpet, maybe some wiring, etc...
Run the engine, check compression if you can. A permanent gas tank that old may have issues with water/sludge but that is hard to check. Good thing they are easily replaced.
Once again, As long as the hull is in good shape and the price is right, and you are aware that you might have to put some $$ in it, go for it. You can probably end up with a bigger boat for a lot less money.