How much you can make from placing articles and affiliate links on your website differs from person to person. How much you are able to make will depend mostly on how successful your site is. This means getting good search engine rankings through SEO efforts, making your site enjoyable and informative to read through engaging content, building your site around a great niche subject, how big your site is, and how many sites you have.
Some people claim to make as much as $10,000 per month ($120,000 per year) through building and promoting niche sites, however, most people should not expect this kind of success, especially if you are very new, as that kind of success usually only comes with experience and acquired skill. A reasonable income to expect from a niche site, after you have worked for months to gain traffic and are hooked up with good affiliates, may be $500-$1,000 per month. However this is recurring income, so you will make that much monthly off of the efforts you put into that one site, it is not a one shot deal.
After you have a successful site, most choose to continue to build niche sites. The more sites that you build, the better an income you can generate. Some also choose to build very fast and very short sites over sites that are slightly longer in length. It should be noted that the larger each of your sites are, the more income you will likely generate off of them.
When starting out, it is important to remember that your first site will always be your hardest, since you are just learning the ropes of the business, and that not everyone is cut out to market and promote niche sites. It may not work out for you and you may end up losing a little bit of money, but that is a risk that everyone in this business has to take.
The important thing is that you don't give up without a good shot at it, if this is really what you want to do. Your first site may take a long time, the work may be tedious, and you may feel like throwing in the towel. However, if you give up too early, you will never know what could have been. And who knows, you may be the next great website marketer!