At what point is a Part 107 Remote Pilot Certificate required?

Anything other than recreational use (flying for your own enjoyment) or use for a public agency (Police, Fire, etc.) would require you to obtain a Part 107 Remote Pilot certificate and comply with those requirements. If you are unsure of where you fall the FAA does have a “User Identification Tool”. https://www.faa.gov/uas/getting_started/user_identification_tool/