In general, the market for discounted loans has shrunk considerably during the past few years because people have refinanced as rates have fallen. Refinancing has caused many notes to be paid off.
Also with many financing options available at 5 percent down and less, the need for seller take-backs, a major source of investor notes, has shrunk.
In effect, there are relatively few notes out there to buy or sell. At the same time, around the country more and more people are taking classes which explain how to buy and sell notes. The result is massive competition and little supply.
If the purchase and sale of notes holds some interest, then work with a local mortgage broker and learn the business. In addition, find out about such licensure and regulatory requirements as may apply to anyone who buys and sells notes.