Hey,
Collecting Comics should be first and foremost a hobby that brings you enjoyment. You are going to buy a lot of books that may gain a dollar in value if anything before you come across that big ticket item. If you are looking for profit I would suggest that you actually invest in stocks via inter-net trading, it's actually quite easy and can be done through any bank. It's nice to have big value items in the collection but it can't be your main motivation for collecting. When you take into consideration storage cost, opportunity cost, inflation (2.5% per year) very few of your books are going to generate a return equal or greater than other options with your money. So again, collect because it makes you happy not for some hope that it will pay off in the back end.
Cheers,
-RKSM