lgn1 - 3:33 am on Oct 4, 2013 (gmt 0)
Get a good book on ecommerce, because the answers to your question, would fill many books.
Here is the Cliff (Cole's) notes version, with most of the pages missing:
You need an niche market. One with little competition but good demand. Find a distributor that will drop ship for you. Avoid Amazon, if you are successful, they will buy bulk and undercut you. Magento is a pig to deal with, especially starting out, go with an integrated solution such as shopify. Prepare to fail. Learn from your mistakes, repeat until successful