This model is do-able but be aware of a few potential problems:
- You may not be able to take advantage of volume discounts if you constantly place back-to-back orders
- Will your image be harmed if suddenly a product you offer is no longer available from your supplier?
- As your business grows it can be more efficient to maintain at least some inventory
You are essentially a middleman as you have described the business in your post. As long as you serve a particular niche well you will be fine. But if you are reselling product that can be found in multiple venues your chances of survival long term will be tough.
All the best,