Keep in mind, these are overarching niches. It’s in your best interest to take a large niche like the ones listed below and find a micro niche within that niche.
Companies that sell their products online often look to partner with bloggers in their niche. Bloggers who work with such companies are called affiliates. Basically, an affiliate blogger helps a company to promote its product and gets a commission for every referred client.

Of course affiliate sites can have a lot of really useful information on them and we like showing them in search. But, at the same time, we see a lot of affiliates who basically just copy and paste the feeds that they get and publish them on their website. It's not something where we say that an affiliate site is bad, we just see a lot of bad affiliate sites. And if you have affiliate links on a website, that's not going to be something that we would count against a website.
For every conversion (often a direct sale), affiliates receive an agreed upon fee. This may be a flat fee ($50 for every sign-up) or an immediate percentage of sales. In some cases, affiliates are only paid for the first sale, while in others they may be paid for all purchases made by a customer within a year, or indefinitely.