Is the money specified by the applicant for the purchase, preparation, and transport of a computer, without informing the owner of the money, lawful or unlawful?

If you are acting as an agent for someone else in purchasing an item, you must inform them of the true price. It is not permissible for you to add a commission to the original price without their knowledge and consent, nor to mislead them into thinking that the price includes your commission. You may purchase the item for yourself first, and then sell it to them at a price upon which you both agree.