Things that needs to start a simple retail business take to time, money, place for shop or office & and good contact and social skills. Now if any person is in student stage of life and want to earn more than its pocket money he/she if starts the retail store or whole store became impossible for them to run both equally in single time. That business sucks their time gave to much damage on their studies. It doesn't means that every one can not to that business some can manage their time for both things but its the better idea that they start the e-commerce site which have less competitors in market.
E-commerce business getting popularity day by day in not only retail field but some wholesalers started to sell their item online. So the question asked by any student how to do that? its easy you now with wordpress, jomla, magento its easy to operate your e-commerce site with them the you need to learn a little bit of Html and Css or Jave script (if you can, its not necessary) by learning them you can easily manage your site and make your own sites on web just you need the Hosting server sites which costs not to much. but for those student who don't want invest money of hosting server and domain, i recommend them to try Blogspot, 000webhost & wordpress. these are the sub domain sites and gives you free space on web for your site.
These all are to simple ways to make your e-commerce store on web you can take guide from youtube by watching tutorials about them and they do not take your to much time, so try to build your own web store