My main concern with wordpress is that i cannot think of a site that is highly successful built off of wordpress.
How do you know this? How would you know if a site used Wordpress strickly as a CMS.
If you dont have the money to hire designers/developers, then you do have the option to learn how to do this yourself, however, with wordpress all that is done for you. You can find a theme you like, or if you feel like you can handle it, you can design your own theme. Then install plugins for your needs, such as databases, shopping carts, social network links, and the like, and you're all set.
By the time you got a good grasp on the different aspects you would need, the idea may be outdated or worse, already done, provided its a really great, unique, and marketable idea.