Ask a training provider how someone buys a course from them today, and for a lot of them the honest answer is: they email you. Then you send an invoice. Then you wait for it to be paid. Then someone manually sets the person up. There's no checkout, no self-serve option, nothing that works at 9pm on a Sunday when someone's actually ready to buy. Not because the courses aren't good enough to sell that way, because nobody ever built a way to sell them that way.
The good news is that going digital doesn't have to mean a big project. It comes down to one thing: finding a platform that makes the administration more efficient, no more emailing back and forth or juggling spreadsheets to track who's paid, who's enrolled, and who still needs a reminder.
If you also want to start selling content online, look for a platform whose payment solution handles the logistics automatically too. That opens the door to selling add-ons alongside your instructor-led courses, or selling fully standalone online courses, checkout, account creation, and course access all happening in one flow, with nobody needing to touch it in between. Once that's in place, selling online is simply how you already work, just without the email back-and-forth.