I just found a pretty niche interaction: a Loan with an Always Be Closing attached. This makes the base price 0$ (because -30 + 30 = 0), which increments to 10$ as soon as you buy it. Because the price is positive, the Loan’s 20% interest actually causes the perk to gain money each round. I’m not sure if this is intentional or not, but if so, it was a neat find.