When starting an online business to sell on eBay or simply to sell online, the hardest part is usually sourcing the products, especially wholesale laptops and other electronics hardware; its even harder to locate them within the UK or EU for easier shipping and less delivery durations.
Sites like WholesaleLaptopsUK.com are one of the top wholesale providers for brand new laptops from Apple and Dell. They are the few business-to-business providers that have easy requirements and their delivery speeds are almost always next day delivery. They simply require you to send them an email with your order details and after that you receive an invoice to make a payment - this is actually a standard procedure for ordering wholesale electronics online.
eSources is also a great site as well as alibaba.com who provide wholesale, but their order quantity is much highier than wholesalelaptops.com, and are usually based from china.
When buying wholesale from any company, make sure you only pay by Wire Transfer or Credit Card as these are safe methods of payment which allow you a safety net of protection from your bank (at least within the UK and Europe, not sure about US laws as they vary from state to state).
Order tracking is not always given when ordering wholesale, but this is nothing to worry about; you can simply email them for a tracking number and in most cases they will be happy to send you it.
If you're looking for other sources to buy bulk discounts from, then its important to understand that for some products, buying wholesale needs to be done offline; luckily, laptops aren't that hard to get wholesale, but the hardest from my experience is getting DVDs (latest box office movies) for resale.
In conclusion, its important to already have business policies and terms already setup before you start selling; and its essential to keep records of your receipts and file your taxes; as most wholesalers do not inform you that you must pay tax. In the UK, you usually get a threshold before you owe income tax, but preparing the paperwork in advanced can be very useful just to show your intentions to your tax office.