Crossing Nogales Border with a Borrowed 6 ft x 10 ft Trailer

I'm planning to cross Nogales at beginning of March, my question for all of you is, if I borrow a moving trailer from a friend what paper work do I need from the owner? or I should get the paper (ownership) changed to my name and when I get back to Canada change it back to my friend's name. TIA

I don't have any experience with this but putting that trailer in your name and carrying all the ownership paperwork sure sounds like the safest option.

That is exactly what he will need to do.  The car and trailer must be in the exact same name, in the exact same format, as the importer‘s passport, drivers license, credit card, etc.  Mexico is very fussy about that detail. To them, Joseph Andrew Smith, Joe Andy Smith, Joe A. Smith, Joseph A. Smith and J. A. Smith are five different people. You cannot convince them otherwise, so be prepared.  You cannot enter Mexico with other people‘s goods; just your own stuff.
However; there might be a simple solution: A Bill of Sale, nicely printed and notarized with all the trailer details. Mexico is mostly interested in its VIN and ownership. When you return the trailer, just tear up the document and it remains the property of the friend, from whom you borrowed it. That might just work.

I wouldn't risk that after driving all the way down from Canada. Just get it put into your name. It's easy to switch back later.

I agree. I was just speculating out loud. Maybe someone closer to the border has done it with a bill of sale & could report on how it went.

And coming from Canada make sure you have a letter from your insurance company confirming your registration and/or insurance document acts as "proof of ownership" and/or "Title". We came from BC and had a letter from ICBC stating our registration acts as Title. And take the "nothing to declare lane" at the Mexican border if you have no new goods and/or commercial goods you are bringing with you. We had our menage de casa (list of household goods) "certified" by the Consolate in Calgary before we left. We brought our Dodge Durango with a loaded cargo trailer in January 2013.