Buying Coins As An Investment

I hear a lot on TV about buying and selling gold, and that now is a good time to buy silver coins. I have never done any of that. And I probably will not anytime soon. But I remember a neighbor of mine used to have a coin collection. I used to look at it as a kid and thought it was so neat. He spent so much time on it, and it was quite a complete collection. I am sure that those coins are worth a pretty penny today. It is probably not something I am going to do for a long time, or ever actually, but it is fun to think about. It would be neat to have a hobby like that that could actually grow in value.