What is the ruling on a business based on buying a car from an exhibition in my name and selling it to another person in installments with a multiplied profit, then the buyer sells it to obtain liquidity? Is this considered exploitation of those in need and a manipulative ploy to circumvent usury?

Investing money in a car showroom is called Mudarabah (definition) (speculative partnership), and for it to be valid, the capital must not be guaranteed, and a common percentage of the profit must be agreed upon. It is permissible to take a portion of the profit on account if a profit appears. However, if no profit appears, what was taken is deducted from the capital. It is forbidden for the showroom to buy back a car from someone to whom it was sold on installment at a lower price; this is known as Bay' al-Inah (re-purchase sale), and it is usury. As for a buyer selling a car on installment at a high price in the market for a lower price to obtain cash, this is called Tawaruq (monetization) and is permissible according to the majority of scholars. There is no objection to the showroom selling on installment at a reasonable price.