The topic you choose must have enough depth that you can create a lot of content for it. This is important for building an authoritative site, for search engine optimization, and most importantly, for the end user. If you don't have enough content about a topic, you're not going to be taken very seriously as an authority on the topic and it's unlikely you can convince someone to make a purchase from you. 
There are many freelance options for graphic designers who are looking to make money online. Designing layouts and graphics for promotional material, corporate reports, magazines or book covers, are all tasks that businesses are looking for online freelancers to complete. Due to its flexible nature, graphic design possibilities can range from one-off projects, to ongoing work with regular clients.
It may take time to build that audience that turns views into dollars. The average revenue per 1,000 YouTube views is just over $6. But with enough videos for fans to scroll through, those views can add up over time. While you're building an audience, you could also join an affiliate program related to your channel and make money through affiliate links in your video descriptions. 

You may have heard of ClickBank, one of the oldest and most popular affiliate networks. A billion-dollar company, ClickBank specializes in digital products like e-books and software, as well as membership sites. If you are comfortable selling information and don’t want the management and administration hassles of “real” businesses, this may be a good starting point. Its commissions can be anywhere from 10% all the way to 75%.
Another way to utilize your talent and business skills is to run corporate workshops online. Businesses are always looking for unique ways to help educate their workforce, and if you can package your talents into a day or half-day long session, you can sell that to companies all over the world to make money online. Start by building a portfolio and then reaching out on LinkedIn to influencers at relevant companies to see if they would be interested in you teaching their team.

There are numerous printing companies that will print your designs onto not just T-shirts, but also hoodies, hats, posters, cushions, bags, and phone cases, to name a few items. These businesses also offer fulfillment services. This means that you promote the merchandise on your own site and once you sell a product the printing company will not only print your design but also send the item directly to the buyer. So all you have to do is concentrate on the marketing and selling of your products, and the fulfillment company will take care of the rest.

Ready to enter the ecommerce fray? Why not sell your own stuff. Of course, along with selling your own stuff on your own website comes a whole slew of both responsibilities and technical configuration and requirements. For starters, you'll need a website and a hosting account. You'll also need a merchant account (sure you can use Stripe or PayPal). Then you'll need to design that site, build a sales funnel, create a lead magnet and do some email marketing.
Win-win-win. The advertiser wins because they only pay when a purchase is made (as opposed to the shotgun approach of paying to advertise to the masses and waiting for a small percentage to actually buy). The affiliate wins because they make money while providing helpful advice. The customer wins because they get a trusted recommendation for something they might not otherwise have known about.
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