Does the ruling of "selling what one does not own" apply to receiving advance payments (earnest money) for digital products, such as recorded or live training courses, by way of confirming a reservation?

The basic principle is that it is impermissible for a person to sell what he does not own, whether the item sold is a tangible commodity or electronic software. However, it is permissible to take a earnest money (non-refundable deposit) when making a promise to sell or lease. As for training courses, whether in-person or online, they constitute a lease (sale of a benefit), and it is permissible to hasten the payment of the entire rent or a portion thereof.