Outbrain is not necessarily the network of choice, it was just an example. As for tracking the ROI usually you'll want to track campaigns in Google analytics and track clicks on affiliate links as event and average value/email or you'll want to duplicate the post and run paid traffic to the duplicate so you know exactly what the conversions are as you can put them in separate email lists etc too.
Most businesses require startup fees as well as a cash flow to finance the products being sold. However, affiliate marketing can be done at a low cost, meaning you can get started quickly and without much hassle. There are no affiliate program fees to worry about and no need to create a product. Beginning this line of work is relatively straightforward.
#2 High Priced. Another downside is that the course does cost more, a lot more. At $997 it does sound like a lot but I prefer not to look at the cost as a burden but rather an investment in my future. The way I see it if this teaches me how to how to build even a modest income of a $1000 per month for the rest of my life I feel the price is well worth it.
When promoting affiliate offers, just make sure you are fully aware of all the terms and conditions attached to your affiliate program. Some programs can be strict about how they allow you to promote their products. For example, some may limit you to banner ads and links only, while others will allow you to use paid advertising, but won't allow email marketing.