A-5's are fine firearms. I still miss mine almost 20 years after it was stolen. There is a vast amount one needs to know about them before buying a used one.
As a quick for instance, a significant number of those on the used market will have a crack/split in the forearm where it mates with the receiver. This is almost always the result of the forearm being improperly re-installed after cleaning, or of improper positioning of the recoil rings around the magazine tube. Examine a used one very carefully before purchasing. Replacement parts will be getting harder to obtain each year. There are a great many other potential pitfalls to be aware of. Some can be used safely with steel shot, but that is another long and involved subject.
A good A-5 is a thing of joy to those who are proficient with and appreciate them. I suggest you do extensive internet research, or better still, find someone in your area who is truly knowledgeable of them before you shell out any hard-earned $$.
For what my opinion is worth, I'd be very wary of a $250-$300 A-5. Caveat Emptor (for those who did not take Latin in high school, that means "buyer beware.")