Where you bring in cash is likewise a very personal thing, I believe. A few individuals build sites that work for banner deals, some don't. A few individuals would like to work with merchants more directly, selling their stuff, other people can't make it work. A few will go to gambling sites, other people want to construct labors of love, indulging their passions and incidentally, utilizing the sites to pay the bills.
Remember that distributing intangibles like info or services is fraught with its own troubles; there may be extra legal issues involved (was the info or service ever delivered? Can you prove it? What if somebody pays for a piece of software, then denies the charge? Can you take the hit?)
Selling goods leads to ramifications with shipping; do you send the tangible stuff, or the merchant? Who manages returns? Who manages customer complaints?
Don't be fooled, operating on the net isn't easy. Pure affiliates have a comparatively easy ride; they simply supply the traffic, and collect the checks. To make up for it, they have to send numerous visitors to make the big money.
Where do your interests lie? That will supply you with the first answer in ascertaining what’s right for you.