Welcome to the forum. Glad to see another from Colorado. I read your other post on getting a title.
Delta99 wrote:To get it titled in CO, I first have to insure it, and provide proof of insurance. Then I have to make an appointment to have a LE officer come out and inspect the trailer. Then I have to apply, and wait for a title. At this point, I've already done everything I didn't want to have to do, so after all that, I'll just get the plates here, and spend an arm and a leg. My dreams of $10 registration through the mail have been shattered.

Oh well
I don't think it is that hard or expensive to register a trailer in Colorado. I built my frame so all I had to do was fill out the home built form go to the DMV and give them a copy of the metal, lights and axle receipts and then I got a temp plate $6. I then went a weighed it at a truck stop which cost $10. You only need proof of insurance on your tow vehicle but not the trailer. I then drove to my inspection appointment. They looked at it checked the lights and in less than 10 minutes gave me paper work to go get title and license. Back to the DMV and $62 later I had it registered, got a small metal VIN number plate to rivet to my frame, and a license plate. I was now legal to go camping. The title came in the mail about a week later.
If you are using a Harbor Freight trailer it should of came with the paper work needed to get it registered.
Good luck with your build
Dan