First off let me just say, the fact that you chose to start an eBay business to sell your products and services instead of a traditional bricks and mortar store, lets me know that you that you understand how businesses are run in the 21st century.

There are so many advantages to starting an eBay business over a bricks and mortar store, that I won't even begin to bore you with the mile long list.

HOWEVER, that being said, you will have to be prepared for a few things. These are usually the kind of things that so many people get wrong. Here is just a drop in the bucket.

Lean how to pack well. Unless you are planning on selling socks, the items you sell will have to be packed professionally.  Don't worry it's not as complicated as you think.  But the days of just shipping items unprotected, and hoping that it reaches your buyer in one piece are long gone.

Customer Service.  There is one great advantage (at least I think so) to selling online, which is less face to face contact. You don't have to schmooze each Tom, Dick, and Harry that walk into your store.  But that doesn't mean that customer service doesn't reign supreme.  In this kind of business, you are going to have to communicate well with the written word.  You want to be as clear and concise to every person you email, as you can possibly be.

Also when it comes to customer service, PLEASE answer your emails right away.  I know that we live in a culture where people don't respond to emails until they feel like it.  That's not going to cut it here.  If you want to succeed on eBay, answer your emails, as quickly as possible.  Trust me when I say that it will definitely increase  your sales. I can't even begin to tell you how many sales I have gotten just by answering a simple email, the instance that I see it.  If you can't do that, then this business may not be for you.

Listing Descriptions.  My goodness!  It's astounding how many people get this wrong.  Have you ever looked at a listing description and thought i was a freaking book!!   When people are shopping online they want key phrases.  They want to know the condition, measurements, new or used, etc.... They don't want read paragraphs on top of paragraphs.  All they are going to do is just hit the back button.