Participate from the beginning. Original team player in a new enterprise. ‘Ground floor’ references the bottom of a tall building, the first building block in an enterprise. So to get in on the ground floor is to start working on a project from the beginning. Especially good position if you work, for example, a start-up hi tech company that earns billions later on. (Compare to From the get-go.)

“I bought some stock today because my broker told me it was really hot and I should get in on the ground floor before the price went up.”