You can opt for a free sub-domain and free hosting and put up a site and make money! - Not necessarily IMO. This would depend on the niche of your choosing.
If you are out to make a decent revenue, you would need knowledge, experience, patience, dedication, creativity and MONEY!
Money to put up a decent site, to spend for advertising, to maintain your site, etc.
Sure there are free ways you could do to promote your site, but it does not mean you will be successful at this especially at getting the right visitors for your site to make the conversion.
Good content + SEO + PPC, Paid back links, Forum posts to similar niche, banners, etc. = Great traffic and more targeted traffic!
IMO, opting for paid ways contribute well to a good marketing mix especially at getting targetted traffic. In reality, getting 10 targetted traffic is better that 100 random traffic. Getting just mere random traffic doesn't constitutes your site's success - it's the conversion you get from your traffic. Getting traffic is just the first step, offering the right stuff to your visitors and conversion and the satisfaction your customers get from your product or service should be utmostly considered as this will define your site's success.
