The economy is showing few signs of recovery, but one area of business is doing well: door-to-door loans. Panorama investigates the debt business, a world of cash on the doorstep and high interest rates. We go undercover to reveal the tactics of the trade: the real costs of a loan and the techniques which mean that some customers may never clear their debt. And we find victims - the vulnerable and mentally ill, who are sold loans in apparent breach of industry guidelines.