Depends on what you are selling.
I've found some things that were pretty lucrative, but profit on each sale was only 50 cents. However I could buy hundreds of these products for $20-50 buying them used. Half the time I would buy the products on Ebay, just by looking for poorly listed lots of the stuff, or someone who clearly doesn't have the time to inventory their entire collection.
It was trading cards actually, something that people really don't have time to get to know or bother to find values. I decided I mind as well since it wasn't overly saturated with sellers and there seemed to be enough buyers.
The only problem is doing what I did took a lot of patience. I basically was only making $20 a month for like 6 months, and once my limits were raised to over 1,000 products a month or 10,000 USD, I actually started making money doing this.
I would literally have 40 listings end every night, and made a nice profit of $100-200 a day.
However the amount of effort it took to find the lots to buy, then inventory them, research them, price them properly, take pictures of them, create a description and listing, crop the photo, post the photo, package the product, and send it out,......... it almost wasn't worth it.
So basically the point of my story is you need to consider how many sales you think you can handle, and how much you want to make off each sale.
I picked something that was cheap to buy and cheap to sell, but I was doing higher volume of sales so I was making enough money, BUT IT WAS A LOT OF WORK. And I sometimes wished I was just selling more valuable items to make larger profits.
The problem with that is it's harder to find reliable sources of more valuable things, like electronics, or clothing. And customers are a lot pickier when spending that much money.
My customers were spending around $5.00 an order(I encouraged spending at least 5 because they would be qualified for free shipping after). But doing that 40 times a day made it worth it, since each item cost me around $0.10 to buy sometimes they only cost a penny.
However, since I had such a high volume I was subject to more risk from being burned by detailed seller ratings. more sales means more seller ratings. Seller ratings are your enemy on Ebay, whether they be good or bad, I would rather my buyers not leave any rating. Most people have unrealistic expectations for what they're paying for, and end up giving you maybe a 4/5 instead of 5/5.
Believe me a 4/5 could be the end of your account if you get enough of them.
I had one prick buy 10 cards off me for a whopping total of $8.00, he decided to give me a bad rating for all 10, coupled with two other buyers who were unhappy with my shipping time, and I was restricted from selling. Regardless of my thousands of otherwise satisfied customers.
People do not leave feedback generally when they are satisfied because it is tedious and boring to do so for the most part. But if you are upset, or at least feel, it took too long to ship, or the seller didn't communicate well, or whatever, you will leave feedback. It may not be negative, but the odd time you get that 3/5, and enough of those can burn you.
So basically;
- decided how much time you want to put into packaging and shipping and listing
- don't ever ask for feedback from your sellers, and list clearly, do not leave a single detail left unsaid, or you will eventually get burned by some moron buyer