You can get some idea of how AmSher will handle collections from the Eight Steps for Effective Collection Calls, an interview with co-CEO Martin Sher.
Prosper lenders can choose which collection agency they want to use. The other options are Firstsource and Penncro. AmSher charges a fee of 17% of the funds recovered while FirstSource and Penncro charge 15% of funds recovered in the first month and a decreasing amount thereafter unless the payment is bringing the account current. You can view historical collection data and change your default collection agency at Prosper.
Most Prosper lenders use Penncro. Penncro has brought 16% of E and HR loans current, 17% of B-D loans current and 19.4% of A or AA loans current.