1
general::
Phrase(s): *in on the ground floor
Fig. involved at the very beginning of something. (Alludes to riding in an elevator that will become increasingly crowded as it ascends. You will be able to get in most easily at the lowest level. *Typically: be ~; get ~; let someone ~.) • If you are starting a new project, I want to get in on the ground floor. • Invest now so you can get in on the ground floor.
McGrawhill's American Idioms And Phrasal Verbs