I've been looking to start my own company for many years now! My aunt owned a storefront in Ohio and because of the major department stores, it went under. She decided to take her store to Ebay and it's been booming ever since!
1) Select what you are going to carry in your store and where you are going to get your stock from. This is going to take an initial investment or you will just have to build up stock slowly. It's best to avoid paying any interest of you won't be making as much because you will have to pad the prices of your items!
2) Select a name for your store. Be creative!
3) Figure out how to market your store. The better your marketing, the better your sales will be!
4) Finances. This is the most important part. You need to consider all the store fees (listing and selling fees) as well as paypal and shipping fees. It's also important to figure in gas prices because it's going to cost you to take your product to the post office to drop it off. Investing in a copy of quickbooks is highly recommended!
All in all, having your own ebay store will be fun and will also bring in extra money which is a great thing!