Do I really need to have my own domain name?
The one word answer is "YES." If you put up your site with some of the free web hosting services, the only company who benefits is the web hosting company. The last person who benefits is you. There are a number of reasons why having your own domain name is a must:

When you have your own domain name, the address of your web site will be of the form http://www.yourcompany.com. On the other hand, if you put up your site on one of the free servers, the address of your web site will be something like http://www.somefreewebsite.com/yoursite/. Which of these two sounds more professional? Which of these two is smaller and is hence easier to remember? We leave you to make the judgement.

The only way to make your presence online is to build up credibility among your customers. Having your own domain name is the first step in doing that. Your customers will feel more comfortable buying whatever it is that you are selling if you have your own domain name. It makes your customers feel that they are dealing with.