People are finding a good investment in a niche of the used car business known as “Buy Here Pay Here” auto sales. In the last two years, investors have bought more than $15 billion in sub-prime auto securities with the hopes of cashing in on profits that average 38% for each vehicle sold. Two of the biggest, America’s Car-Mart Inc. and Credit Acceptance Corp., have seen the biggest gains well above the regular market.

The Buy Here Pay Here vehicle market focuses on helping people buy a vehicle when they can’t qualify for conventional loans. Because the customer is a risk and can’t get a loan anywhere else, the dealership can get away with selling the vehicle for more than it’s actually worth, charge interest rates up to three times the national average, and use aggressive repossession tactics when the customer defaults. Because Buy Here Pay Here businesses are both auto dealers and consumer lenders, it’s not always clear who has authority over them. As a result, each dealership tends to set their own rules.

Although they’re backed mainly by installment contracts signed by people who can’t even qualify for a credit card, most of these bonds have been rated investment grade, some receiving the highest ratings. But so were the financial strategies that drove the nation’s recent housing bust. “We think that investing in such companies is a ticking time bomb,” according to Joe Keefe, chief executive of Pax World Management, “It has ethical as well as systemic risk implications.”