Considering that you have a finite amount of time, passive income should make up a large part of your work. If you're serious about generating any semblance of income online, then passive income should be one of your sole goals and ambitions. Why? Wouldn't you prefer to do the work one time and get paid repeatedly as opposed to relying on your time to generate that income? Invest the time at the front-end so that you can reap the benefits on the back-end. This means putting in a bit of sweat equity and not getting paid today. Rather, you'll get paid somewhere down the road. And you'll continue getting paid whether you keep building that passive income stream or you stop. 
Being in Australia, I’m not required to do anything by the law (although I hear talk that there may be changes around this). I don’t disclose every single Amazon link on my photography blog in a direct way but do I have a disclaimer/disclosure page on the blog. When I’m doing a ‘best seller list’ always include a disclaimer on those posts as the whole page is filled with affiliate links. I have also written numerous times on DPS about how the links to Amazon earn us money and help the site to keep growing and be free.
1. Commerce: Two parties are affiliates if either party has the power to control the other, or a third party controls or has the power to control the both. Affiliation also exists in (1) in interlocking directorates or ownership, (2) in identity of interests among members of a family and, (3) where employees, equipment, and/or facilities, are shared. Affiliates are subject to greater than normal legal prohibitions and requirements to guard against insider trading. See also subsidiary.
It has universal appeal. Unlike some types of marketing that work better for certain segments than others, affiliate marketing is really something that anyone can use on their WordPress site or e-commerce store. With millions of products available and categories covering a wide spectrum, you’re bound to find more than enough products worth promoting.