The majority of websites that are created to make money exist to promote products via affiliate programs. The advantage of affiliate programs is you don’t need a product of your own, and you don’t need to worry about dealing with customers. The disadvantage is you will not profit anywhere near as much as the person offering the product.
Say for example you joined an affiliate program to promote product that sold for $100. So you are paid a 20% commission, which is $20 per sale. If you paid for Google adwords, you would need to get one sale for every $20 you spent. That won’t be easy considering there are likely other people selling the same product. My take on affiliate programs is they are not much different from pyramid programs, where the person at the top makes the majority of money. If you have already have good advertising reach, then it is a good idea to use it to promote other people’s products provided they don’t directly compete with yours. But in my experience, creating a site specifically to promote other people’s products is not the best way to go.