Monetize a hobby. While some hobbies actually cost money, others can be transformed into a profitable business venture. Ultimately, it depends on what your hobby is and how talented you are. You could turn your love of photography, for example, into a part-time gig taking family portraits and wedding photos or selling prints on Etsy or at arts fairs.
The IM and MMO niches have higher refund-rates than the other 298-ish niches represented at ClickBank (but there's little point in promoting any of those as an affiliate anyway, for the reasons explained here). Other than that, the refund-rates vary enormously between different affiliates for the same products, because they're mostly determined by how the product is pre-sold.
Whether you have a website or are still dreaming up ideas for a blog, you can also look into affiliate marketing. With affiliate marketing, you partner with brands and businesses within the content of your website. If you mention a product or service, you link to that produce or service using a unique affiliate code you received when you signed up for that particular affiliate program. From there, you’ll make money any time someone buys a product or service through your link.