I don't know too many funders that can be very profitable with a 15% default rate.

A-B paper default rate should be 5 - 8%

C-D paper default rate should be 9 - 13%

From my experience once you go over 13% default rate it is very hard to turn a profit. Cost of money, overhead, commissions, advertising etc... Will not allow you to have a default rate above 13%. Unless your average turn time on deals is under 5 months, closer to 3 months then maybe the D paper shops can stomach 13% + default rates because they're turning their money 2.5 - 3.5 times a year