You need a CDL if:
your gross weight is over 26k
If you're towing a trailer and the combination wt is over 26k, provided that the trailer grosses over 10k
So, if your trailer, fully loaded, plus the truck can exceed 26k (whether you have that much on the trailer or not), you need the CDL. Even if you register the trailer for less, they will go by the manufacturers gross weight.
Your truck weighs roughly 6k. If your trailer is designed to hold 20k, you need the CDL no matter what's on it or what it's registered for. If your trailer is designed to hold 19k, you're off the hook because your gross combination wt is under 26k.
Yes, you need a physical and to keep a log book.
This is all for interstate travel. Intrastate is a lot lighter and varies by state.
If your passengers share the driving, they will also need CDL's, physicals, and log books.
