Whether your goal is to boost savings, supplement retirement income or pay down debt faster, you are not alone in choosing to work nights, weekends or in-between other demands.

This can mean Uber driving, dog walking, freelance writing, even assembling IKEA furniture for a fee, essentially wherever skills and interests intersect with demand for those services.

The U.S. Bureau of Labor Statistics says about 20 million Americans are working part-time for so-called “non-economic reasons,” meaning issues such as childcare or income restrictions prevent them from working full-time or they simply do not want to work full-time.

One topic close to the classic “side hustle” is passive income. But what is it and how does it stack up to other types of earnings? The concept is called passive income because it requires little to no time on your part, yet can yield some serious recurring money.

If you have a website or own a domain name, joining a CPS affiliate network is relatively easy and there are some very good and reputable affiliates, including Amazon and eBay. Lesser-known affiliate programs are just as noteworthy and can generate revenue for use of your website as well. We’ll get to that list in a bit.

First things first, though: consider if your website is poised to become an affiliate website. Are you an authority on a particular subject? Does your website focus on a definable niche?

Determine Your Audience

If you can say “yes” to either one of these questions, your next step is to evaluate what kind of affiliate advertising would parallel your mission and serve your visitors. For example, writers and linguists who visit Grammarist, a website for word junkies and students surfing for extra grammar help, will find a banner ad for Maxwell House and Adobe’s Creative Cloud. I guess they think people who write love coffee and cool technology. (Right on both counts.)

Assume it’s a successful pairing, you’d be paid on the basis of clicks, purchases or leads that come from your pages.

How Affiliate Websites Work

The affiliates provide all the marketing muscle you might need, including banner ads, logos, tracking applications and tips on how to optimize your site to attract more viewers, and ultimately, clicks. Most have a team of managers who will help you get started and make sure you are on the right path. The goal is for your website to drive people to purchase name brand and not-so-name-brand retail products.

Additionally, some affiliates compensate you for posting on Facebook, Tumblr, Twitter and other social media sites. Taking this a step further, some will pay you for sending out links via email. One thing: if any affiliate marketer asks for money upfront, shut them down. You should never have to pay someone else to host ads on your website.

Related >> Reader Story: Turning a Side Hustle into Self Employment

If this is something you are looking into as an additional household or business revenue stream, I would recommend talking to the affiliate’s support team, asking a lot of questions, giving it a test run and determining how much time and energy you are expending relative to the actual return on investment. The key is building traffic to the sales page. For example, if you are a blogger and the ads are on your blog page, the more you promote your content, the greater your return as an affiliate. Use your affiliate link in the target page URL ad on Google Adwords too.

Here are some networks you may want to consider.

Noteworthy Affiliate Networks

The Blue Book Top 10 affiliate networks (in alphabetical order) for 2016 are:

Amazon Associate Network is offering up to 10 percent fees for selling the various retail product offerings on its site.

Avangate claims its merchants offer commissions up to 75 percent, special bonuses, and payment for licensing services.

AvantLink stresses quality over quantity and does not promote gaming or adult content sites. Ten years in business.

CJ Affiliate by Conversant allows its affiliate publishers to post retail coupons, set up email campaigns and distribute links to third party affiliates. The business model is based on loyalty or rewards.

ClickBank sells lifestyle products created by “passionate” entrepreneurs and claims to be a top 100 internet retailer.

eBay’s Partner Network currently is offering double commissions for the first three months that you join its affiliate network. Just post interesting items that you find on eBay to your blog, website or social media sites and you will receive a commission for each time an item sells.

LinkConnector offers fraud-free protection. Has been in business more than a decade.

Rakuten Affiliate Network claims it’s a Top 3 e-commerce company in the world. Offers more than 17 million products.

Revenue wire’s Affiliate Wire claims it partners with the best advertisers in the industry, as well as with the best software and digital merchants.

ShareASale focuses on technology, service and community responsibility. In business 16 years.

These are not endorsements. Rather it is a quick review of the affiliate marketplace and the major players within it. Please do your own research before signing up with any affiliates.