Printing on demand with advanced payment

Assalamu alaikum.

My question is regarding print on demand. The process goes like this:

  1. I design a t-shirt or hoodie or a similar product
  2. I upload my designs on to my website and social media platforms
  3. I also upload the same designs to a print on demand website and connect it to my website.
  4. I also pay the POD website in advance. Say I load $100 dollars to my “merchant account” in the POD website.
  5. If the price of product charged by the POD site is say $10 (including shipping, fees etc), I advertise in my website the product price as say $15 and I get to keep the difference of $5
  6. When a customer places an order in my website, the POD agent deducts $10 from my “merchant account” and then prints and sends the product directly to customer.

Now is this halal as the products I advertise on my website are already paid for in advance to the POD agent in form of deposit and also the delivery is guaranteed and there is no discrepancy in that regard.

Jazakkallah khairan