Am I considered to have acted wrongly or unjustly, and do I bear a sin, after I covered the full cost of the merchandise from my own money due to my friend's inability to pay in cash, with her agreement to a 5% increase, even though I received the amount from her in installments, and after we were forced to close the shop?

1. It is permissible to agree on a salary and a percentage of the profit in exchange for managing the shop.

2. It is permissible to sell goods in installments at a price higher than the cash selling price, provided that the increase is not separated from the price; rather, the total price is stated.

3. If the seller and buyer agree on the price of a present good, and then the buyer is unable to pay, it is not permissible for the seller to increase the price in exchange for installments; this is forbidden usury (riba). However, if it is a new agreement, then selling in installments with an increase is permissible.

4. If you pay the cash price of the goods to the seller and then take the price in installments from your friend, there is no harm, and this is considered a loan to her if she is aware. If you pay the price including a 5% increase, there is also no harm.

5. However, if you pay only the original price (100) and take (105) from your friend, this is not permissible because it is a forbidden purchase of debt and is considered usury (riba), and the excess must be returned to her.

6. There is no need to feel guilty as long as honesty and good counsel have been achieved in the management and dealings with the friend.