If you can get product nobody else has, or get what everybody else has at a lower price, you're in business. Otherwise, it's going to be tough. You need to start out by defining what's going to set you apart from your competition. That's pretty much the deal with starting any new retail business.
I don't completely agree with the red part of your statement. There is one fairly well known online dealer that I would never do business with again that frequently has unique stock at a good price. Communication is so poor I don't care what his stock or pricing is.