You have to be creative and think outside the box to get ahead of the game. Most people do retail arbitrage, go to thrift stores and garage sales to resell. There is nothing wrong with that but chances are most of your competition is doing the same thing.
Most universities have their own marketplace kind of like Craigslist. Try to find and get access to the local university marketplace. It is full of products that you can sell on Amazon and eBay.
Students are always in need of money and as the quarter/semester winds down they are looking to get rid of their items. Look for the international students who graduated as many of them are moving back to their countries. They typically like to liquidate everything for a reasonable price including their cars.