A question: Are you a potential scammer looking to fine-tune your act?
I'm not trying to be insulting. It's just that being in New Zealand and therefore needing to work through an agent Stateside is only a minor variation from the typical scam setup, which features an oceanographer at sea, or a roughneck on an offshore oil rig, or a soldier deployed to the Middle East, or someone otherwise isolated so the deal can't be done face-to-face. So, even if you're a legitimate buyer, you'll scare off some potential sellers who think
you're a scammer.
One way to avoid being mistaken for a scammer would be for your Stateside agent to be an attorney, licensed to practice in the state where the sale will take place, and to grant him limited power of attorney in writing, thus legally permitting him to act on your behalf for the purpose of the trailer purchase and export only (hence the
limited power of attorney). I recommend using an attorney because the seller can verify that an attorney is legitimate simply by checking with his state's Bar Association. That in itself makes him more acceptable than most private parties you could use as an agent. Plus, an attorney under contract to you can legally handle such niceties as setting up a Stateside escrow acocunt to pay for the trailer, and arranging for export.
A word to the wise, there have been scams where a bogus law firm has been named as an agent for a sale, both in cases where it's a seller who's unavailable to do the deal in person, and when it's a buyer who's unavailable to do the deal in person.
Always verify a law firm is legitimate through the state's Bar Association before doing business with them!
To avoid a scam where someone is trying to sell you a trailer that doesn't exist, or that is not his to sell, the first thing is to insist on being told a Vehicle Identification Number (VIN), and a license plate number. With these, the attorney you hire as an agent can check with the state Department of Motor Vehicles and verify: (1) the owner's name and domicile address are correct, and match what you've been told; (2) the license plate actually belongs on the the trailer that has that particular VIN; (3) the title is unencumbered by any liens.
That should be enough to start with. The details of how to hand over the money and take possession of the trailer can be left as an exercise between you and the attorney you hire.