"All trailers in CO must be registered/license plated, right? How's the process for a homemade trailer work?"
fill this out, take it and some $ to the DMV: http://www.colorado.gov/cs/Satellite...&ssbinary=true
Last time I did that I had a crappy kit trailer from Harbor Freight. I tried to register it with the receipt from buying the kit, and the person told me it was worth more since I assembled it. I blew up at her, told her there was no ****ing way I was paying tax on my own labor. Supervisor came out, blah blah blah, I ended up telling them that I charged myself .735 cents per hour and had 11.435 hours in (0r something like that), do the math a-holes. It went on for a while, then other people started making fun of him, I finally paid tax on the receipt price.