What is the ruling on establishing an online store to sell tangible products that I do not own, where I purchase them and ship them to the customer from international stores after he buys them from my store, knowing that these websites are reliable and I have complete information about the products available there? Is it permissible to sell products in this manner at a higher price than what I paid, or to set shipping fees that cover the product's value and profit, with the buyer's knowledge of the final price?

It is not permissible to sell goods before owning them. The ways out of this are:

1. Salam sale (forward buying): You agree with the buyer to sell him a described commodity that he will receive from you at a specified time, and he pays the price immediately at the contract session.

2. Agree with the buyer to bring the commodity to him from its owner for a known commission, thus becoming his agent, and you clarify to him the price, shipping costs, and commission.

3. You agree with him to bring the commodity he desires, and you buy it based on his desire, then you sell it to him after owning it. It is permissible to take a sum from him before buying as a guarantee of his seriousness, and it is permissible to take a down payment (earnest money) to the extent of the actual damage in case of reneging on the promise.

There is no harm in buying cheap products and selling them at a higher price, or buying expensive products and selling them cheaply and profiting from the shipping cost.