I don't know NY (see DMV comments) but usually it's related to the purpose.
- If you are doing commercial work, you need a commercial plate (and possibly CDL drivers license)
- If you are doing it for personal use, you generally don't.
This is why it's common to see a grandpa without commercial plates (and likely without CDL) driving a big diesel pusher which is really just a commercial tour bus outfitted for living...but tour buses carrying 40-50 old folks for a color tour in the fall will be commercially plated and the driver will have a CDL.
As mentioned, it can vary by state though states are obliged to accept out of state drivers/vehicles if they are legal in their home state.
