Yeah, I think that question is a little too naive and vague. Too many questions...
Wholesale or retail?
You offering warranty/backup?
What can you offer that the competition can't?
Price? Service? Makes and models?
Let's put it this way....from Guy Kawasaki...
If you think of a graph with value to the customer of your product on the vertical axis, and uniqueness on the horizontal axis, you want to be like George W Bush, high and to the right. Meaning you want to offer a product that is of high value to the customer, that no one else is offering or that no one else can do.
If you are doing something that has lots of competitors (not unique) but it of value to people then you will ALWAYS be competing on price. It will be a high volume low margin business.
PS: See Guy Kawasaki's the Art of the Start on youtube...