Most trainers accept payment at the end of a session if the client is paying for each session indivdually. But most of us seem to prefer clients paying for multiple sessions in advance. I will allow clients that have been working with me for a long time to pay whenever they want for as many sessions as they want. It is rare that I don’t get paid for multiple sessions in advance.
But I also require clients to schedule sessions at least a week in advance. And I require 48 hour notice for cancelling a session. I don’t waiver from this policy as doing so would be unfair to other clients and myself. Again, it is rare that I need to deal with this issue.