If you're serious about making money online, start a blog. Blogging is one of the easiest and most sustainable income sources. As long as the blog is setup the right way, in the right niche, with the right content targeted at the right audience, and the offer is complementary to the content, you could make a tremendous amount of passive income from a blog.
Cost per action/sale methods require that referred visitors do more than visit the advertiser's website before the affiliate receives a commission. The advertiser must convert that visitor first. It is in the best interest of the affiliate to send the most closely targeted traffic to the advertiser as possible to increase the chance of a conversion. The risk and loss are shared between the affiliate and the advertiser.
Is this course we're going to explore the world's oldest & largest affiliate marketplace Clickbank. Of all of the affiliate marketplaces there is this is the only true level playing field for every online marketer. No matter if you are brand new to product creation or not you stand an equal chance at making a success online by having your products listed in the Clickbank marketplace.
Again, if your blog has a large reader base, then businesses may be interested in paying you to review their services or products. Not only will you get a free trial using whatever these businesses are selling, you will also get a fee for writing them a review and posting it to your site. Paid reviews (and other paid and sponsored content) can be big money, so advertise this service on your contact page to generate business.