If you have not sold items on eBay before, I would suggest that you start with your own household items that you are ready to get rid of. You likely have things in storage, items in the back of your closet, or things you don't use anymore. You can generally get a lot more for them on eBay than you can by having a boot sale.
Once you get your feet wet with the selling process, and exhaust your personal resources, you can look to local auctions for more items to sell on eBay. Many local auctions specialise in property, personal estates, antiques, cars and other collectibles. Sometimes you can even find large lots of inventory or product types, and acquire the entire lot for a discount or wholesale price. You can then sell the products individually through online auction, and flip your investment into a sweet little profit.
The goal is to buy low and turn a tidy profit. What I have done in the past, and would highly recommend, is that you twin up with your spouse or with a friend. One stays at the computer while the other travels to the local auctions, and you stay connected by mobile. Then you can hunt the collectibles, treasures, strabane and property you're interested in effectively. Remember that your target customer is one that's local, and you'll be sure to find the derry airport somebody is willing to part with money for.