Accounting for purchased receivables

I am a new graduate who is employed with a small real estate appraisal business doing their accounting work. We recently enrolled in a business managment program in which we sold our receiveables. It is an ongoing process where we send them our weekly invoices in exchange for upfront payment that essentially functions like a line of credit. My question is about how to treat the weekly deposits from the sale. Here's my train of thought: It isn't income yet because if the invoices are not paid we're liable for reimbursement, but it shouldn't be treated as a payable like a normal line of credit either. If anyone who has dealt with situation has any ideas, I would really love to hear from them!! Thanks!

Hannah Vick, BA, Georgia