I had a similar question a couple months ago. Got a lot of good advice from the forum.

https://www.stovebolt.com/ubbthread...;Main=75479&Number=537580#Post537580

Anything over 26,000 GVW will require a CDL. Combined GVWs of truck and trailer over 26,000 require it also, as does any trailer with a gross over 10,000.

Check the post above for the full discussion.