Yes, affiliate marketing is a good place to start. Then, as you see what you enjoy the most, you can take different routes. If you are artistic, you might design digital products or sell print-on-demand design products (t-shirts & gear with your designs), or possibly design graphics, logos or fonts. If you are technical you might want to design websites or develop smart apps. You can even resell domain registrations, web hosting, servers & security certificates. You can setup a web directory and sell advertising, but then you have Google as a competitor and they will very definitely be evil.
Believe it or not, I am doing all the above. Plus now I am starting the long process of setting up a brick & mortar web host/server site.
But there are many different ways to start. Your expertise is what is important, so pick something you enjoy doing, something you have a passion for. If it is writing, write an e-novel or how-to do-it-yourself manual, or whatever you are best at.
The main thing is content. You really have to come-up with a lot of it, so if you are into photography or drawing, start there.
There are good free website builders that create really nice, simple and optimized websites, like Mobirise (though you have to pay to take advantage of advanced features like premium themes, PayPal shopping cart, HTML/CSS coding). But they have lots of competition, too. Almost every web host has a free website builder and they have gotten easier to use, as well (though often they can be a little harder to figure out, they usually have great support staff). Probably, the best site builder and content management systems is MODx or SimpleCMS, but WordPress is usually a free install; a simple click-to-install web app (script), no matter the host, that uses a pretty easy design/management system, although you do have to keep it up-to-date (meaning if you don't keep the software up-to-date, which is easy to do, it will likely be hacked because it is so targeted by hackers due to security holes always being patched).
For promotion use friends to help spread the word and social networks to post new updates, news and changes. Announce yourself on Press Release platforms whenever you have newsworthy content, updates, new products, etc.