Once you have your business established the natural trend is to try and grow it. Top eBay sellers call this scalability. I am not sure if that is a real word or not, but it means is your business designed in such a way that you can scale it larger simply by adding more products and/or more auctions.
More Products: The ability to add more products depends on your product niche. If you are in an extremely narrow niche such as collectible depression glass then you have to find a lot more depression glass to grow your business. This presents two problems. First, it can be difficult to find rare collectibles. Second, if you do, you run the risk of putting too much similar product into the marketplace (eBay) and depressing the prices. You have just become your own competitor. The obvious solution to this problem is to expand into a related niche such as collectible carnival glass.
If you work in a niche that has lots of related products, rather than just getting more of the same products which could possible depress prices by increasing the supply, you would want to expand into related products that the same customer would buy. for example if you carried a line of high-quality dog collars and leashes, you could expand into grooming tools, dog-training books, dog beds, car ramps and car carriers and so on. You don’t want to go as far as becoming a general supplier of all dog-related goods or you will be competing with Petco. You would want to find an example of each of these items that has some uniqueness to it such as an original design, or low cost, or very high quality and so on.
The other way to scale your business is to raise your ASPs. There are several ways to do this. You can move up the quality scale to higher-priced items in your niche, or you can start selling sets of things instead of individual items. Back to the dog collar example, you could offer a matching dog collar and leash as a set instead of selling the two products separately.
One woman sells bird seed. No one wants to buy a year’s worth of bird seed at one time, so instead of selling single packages, she sells a deal whereby your order enough seed for the spring and summer season and she mails it to you in three separate shipments over the season. She makes one larger sale rather than three small ones and she has the customer’s cash up front for the larger sale but she doesn’t have to ship 2/3rds of the order until later.