Normally, you shouldn't use a factor beyond the growth spurt that initiated the need for one. You use a factor to get to better terms. And terms, of course, vary greatly. The factor generally discounts the full face value of an invoice by a certain percentage. Rates are generally determined by risk and volume.
High risk is more expensive, low risk less expensive.
Low volume, measured in dollars per month financed, is more expensive, high volume less expensive. If a client can guarantee it will need factoring for a specific amount of either time or money, the rate can also be lowered. Some factors provide annual APR rates which are tied to the amount of financing outstanding, while others simply discount invoiced amounts between two to six percent. Partly because of its unregulated nature, it is rare to find two factoring companies which operate entirely alike. Each factor has its own method to sort out credit issues, notify a client's customers, and verify that invoices are real and collectable.