Webinars are quite possibly one of the most potent ways you can make an exorbitant amount of money online. You'll need an audience to train and you'll need to know what you're talking about. Of course, this usually requires having a website and some semblance of an online presence. However, people can still do webinars without all of that. For example, you might have a sizable social media following and you train them every week on something to do with social media. But you will need a product to embed and sell at some point. Don't worry about it in the beginning. In my experience, the best webinar platform out there is GoToWebinar. 
Can you make money with affiliate marketing? The short answer is yes, affiliate programs can earn extra money and even a full-time income from home. The long answer is a little more complicated. Like any home income venture, success comes not so much from what you choose to do to make money, but whether or not you do what needs to be done correctly and consistently.