Yes to both questions Emma. It takes time to learn the basic skills for affiliate marketing yet once you have those skills you can make as little or as much as you like as long as you are patient.
Re aff marketing: There are so many ways you can go. If you are serious I recommend doing some research and joining a membership site like Chris Farrells or AMZ Amazon Academy (both on clickbank.com) or Mark Ling's "Affiloroma" etc etc. All these guys give you a step by step video tutorial proven system to follow in your own time and they are suited for newbies to intermediates.
Re eBay: Programmes like "eBay Arbitrage" are proven systems but if you do not want to spend your time at the Post office then buy a course that teaches you how to sell via dropshipping.
I make money from Adsense, eBay, Clickbank & Amazon so they all work if you are willing to learn and put in consistent action. That is the key to success & $$$.
One last thing. Its a good idea to market a memebership site like those mentioned above because then you will earn residual affiliate income rather than one off sales.
If you have anything else you'd like to know Emma feel free to message me through the Hubpages contact system.
Hope this helps
Cheers, Barry :)