OK, you have a few primary issues to over come.
1. When dealing with a manufacturer direct, you will need to be prepared to buy in large volume.
2. When selling B2B (Business to Business), you will need to establish a volume sales platform for the customer to choose from
3. You can forget margins of 10,20% and so on, you will be selling in wholesale volume, so your margin will need to be low as your profit would be
made on turnover. That said, the best way to know where you will need to set your margin is to talk to the business's that you are wanting to
supply. Ask them what they are currently paying for X amount, once you know that number, then you will know where your margins will need to be