The first thing you need to do if you're going to be successful online is find your niche. A niche is a category or, something you're going to thrive off of. What you need to do from there is decide how you're going to sell your product.
For step two, you will need to figure out is how to get your hands on your product. How will I get my hands on a bunch of cell phones that I can resell? Seeing how making them is not a very good option, how about buying them from a cheap source. Craigslist and Kijiji are great for this exact thing. You simply search "cell phones" in your local area and ads for selling cell phones will appear. The reason Craigslist and Kijiji are great for this is because many of the people selling on the two sites want quick cash now. In other words, the sellers are not willing to wait for an eBay auction because they need the money right then and there. Arrange a meeting spot with the seller and offer to pay cash, sellers usually like that.
Step three is simply go home, take a picture of your newly acquired cell phone and put it up for bid on eBay with a starting bid of more then you paid for it. I recently came across a used Nokia camera phone on Craigslist for $60.00, I searched the exact same used Nokia camera phone on eBay and it sold for $110.00, a profit of $50.00 for just the one phone.
Buying and selling using Kijiji and Craigslist is a great way to start off an online business. Remember you don't necessarily need to use cell phones, any electronics in general work great such as video game systems or IPods. If you can make roughly $50.00 in profit per sale you make, this is definitely one of the best ways to start off a business or to get some extra cash.