I agree with Dol - put your focus into your business and have great content on your website. The time commitment for a successful blog is huge, and at the end of that all you've got is a great blog and a small amount of money. Put that same focus into the business itself and you've got a great business and (hopefully) a large amount of money.
You have to start with great content, not from a pov that it's there to promote your business. No-one will read that - it's just advertorial. You also have to put a lot of time into it, blogging daily or every two days, responding, commenting, making comments on other blogs, x-promoting on twitter, using your twitter feed to make non-blog specific comments, etc.
Your post confused me though, is your business idea to have a blog? Because honestly, if your business idea is to have a business, focus on that rather than the blogging. If your business is to blog then you have to work very hard and be very lucky - there are 450 million active blogs out there. In that sense, yes, it has been done to death. But a good, innovative business will thrive - so put your energies into the right place.