There are very few ways of earning a decent living on line and many 'tales' are apocryphal (Ebay millionaires etc.). If Amazon and LastMinute are only just making a profit (the reports seem to ignore the years of mounting losses) there is little hope for the Great Unwashed.
Ebay seems to be one of the better bets but you need stock to sustain a regular income. You also need to know what people want. I would imagine that most people on Ebay just make beer money or a single killing that is never repeated.
99.9999% of all the 'set up an affiliate website', 'fill surveys and earn £££££'s', 'host a website' etc., are utter garbage and anyone with half a brain will see through these scams immediately...unfortunately there are a lot of people with much less than half a brain that get taken in by these cons.
To be blunt, I do not know any way of making a REGULAR and REASONABLE income online unless you are flogging goods that are a) much cheaper than elsewhere, b) flogging goods that no one else has (you will also have the requisite lack of customers)or c) providing a local service (car tints, valeting etc., although you would be much better advertising in the local rags.
I'm afraid the Intenet is not the Golden Goose of ancient legend.