Hi, Lisa.  My first question is, do you have a long-standing relationship with this reporter?  If so and you know him/her to pay, I would consider it, especially if this is your bread-and-butter client.  However, it wouldn't be unreasonable to tell him/her that this would cause you a hardship and assert that your current arrangement is your preference. Just because someone else is billing monthly doesn't mean that you have to.  You are self-employed and have a right to timely payment.  The slow season is drawing to a close and there will be more reporters looking for good scopists.  This reporter is not the only fish in the sea.

My main reporter that I work for pays me when she gets paid.  Because she freelances for three different agencies, sometimes it will be two weeks (or a little more) until I get paid for a certain job.  I bill after each transcript to an e-mail address set up specifically for invoices.  When she gets paid, she goes through the invoices and pays for the jobs she just got paid on.  This works for me because she sends me so much work.  I typically get paid every two weeks this way.  I don't know if this is helpful to you or not, but I certainly hope so.  Good luck.