My clients all pay in advance. If they take a series of single sessions, they pay for three sessions at a time, if they take a package, they pay for the entire package in advance. The purpose of my policy is so that I can simplify my accounting and bookkeeping, not have to be in the business of “collection agent,” and can readily enforce my “late cancellation” policy without having to try to “collect” the cancellation penalty since I am already paid in advance.
Of course, each trainer conducts their business according to whatever fits their needs and business model, but this is how I’ve done it for over 18-years, and if I conduct my business consistently with all of my clients, they come to know what the expectations are, and to act accordingly. I find that clients will adapt and follow the rules and procedures that you have for your business if you consistently apply them.
I hope that this helps.