Try affiliate marketing. It's mostly free, there is a massive selection of products, low or no overhead, and all you do is raise awareness about your site and bring traffic to it. This in itself can be a daunting task, but if you are looking for low start-up costs this is definitely a great way.

If you look at my site, EnkiTel.com, you will see that I have chosen telecom as my focus product. I try to keep the site as much focused on telecom as possible. I am actually a master distributor for the calling card company I market, but even if I was not, marketing the product of a successful company is often better then spending time and money on creating your own. All the overhead costs are covered. All you do is invest in marketing and client development. Essentially you are an account manager for these companies.

People spend years agonizing over what to sell or market. Yet the answer is very obvious: take a successful product and find a better way to market it, or any way to market it. If you succeed then you can start thinking about your own product with a base of customers you already have who trust you and will buy from you.

The internet is constantly growing, something like 2 million new subscribers sign on every single week. That is a huge number of potential new site buyers and visitors. Exploit the internet to your fullest capability. If you have time, spend it building your online community, make your site relevant to a topic, and get the traffic rolling. Once the ad revenue starts coming in, you'll have to do your own R&D.

There is no question that building a successful web presence with targeted traffic can take months and years. It can even take hundreds if not thousands of dollars if you want to somewhat speed up the process. However, in the long run, if you stick with it you will see results.