My name is Cordell Wabeke and I am the owner of Majestic Comics, Ltd. I have been buying and sellling comics since 1986 via mail order, retail outlet, and on eBay. These are just a few of my thoughts regarding the buying of comics, pulps, and magazines on eBay.
There are a lot of novice collectors and folks that would like to become more involved in collecting comic books, but are afraid of getting burned by buying online. Here are a few of my own basic rules that I follow when I bid for or buy comics online.
1. If there isn't a photo on the listing I always send the seller an email aksing to see a nice high resolution scan or photo. If I can't get a picture I just don't bid. Have I lost a few good deals that way? Probably. But I've never been burned either and in my book that makes up for missing an occasional deal.
2. I always bid based on the true condition of the book. There are a lot of listings that say something like "Very Fine but..." or "this would grade much higher if it weren't for...". I always stay away from problem books because I am rarely satisfied to have them in my collection and they rarely increase in value at the same rate as a books without problems such as a broken spine, brittle edges, rusty staples, or a detached cover/centerfold, etc. If you're buying to resell or for investment problem books are not the way to go.
3. I only bid/buy what I can afford. There's always going to be another one of what you're looking for on eBay if you're patient. I don't care if it's an Action Comics #1, The Shadow Vol. 1 #1, or an Amazing Fantasy #15 there will be another one listed eventually.
4. While I have dealt with thousands of buyers and sellers on eBay, I do tend to stick with those sellers that have consistent grading, good packaging, a solid return policy, and reasonable shipping rates. I highly recommend developing strong relationships with sellers that you trust in order to avoid getting burned.
5. I have discovered that even if they say otherwise, the vast majority of sellers really do have some idea of condition, rarity, and the latest guide price. This is very obvious on those listings that have little or no description but still have a reserve price. If a listing is lacking a description then you need to ask the seller a lot of questions. If you get wishy-washy answers in return the stay away!
6. Get Educated! I cannot emphasize enough that any new collector needs to become familiar with the terminology and accurate grading characteristics of comics, pulps, and magazines. In my experience comics, pulps, and magazines are about as loosely graded as any collectible on the market. What is Very Good to one dealer my be Very Fine to another. You'll want to keep a journel in order to compare the grading among the sellers that you're dealing with. If you get a book that doesn't match up to YOUR criteria send it back for a refund. Condition is everything when it comics to comics, pulps, and magazines whether they're old or new.
I know these are only very basic tips and rules, but as you become more experienced you'll realize that they are a very solid starting point for the beginning collector. Just remember it's not the amount of money you spend, it's whether or not you have received a good value in return.