I never thought I would be commenting on how easy it was to do anything through the DMV in any state, but that was my experience. It did take a couple trips, but relatively painless. The trick was to call ahead and find out what I needed ahead of time. I had the frame custom built.
1. Go the the DMV and get an "NCX" number for a homebuilt trailer. They give you a paper with this on it that the inspector in #3 has to sign. This takes $5 in cash.
2. Have the NCX number stamped on the axle and the tongue (I did 1/4" letter size).
3. Go to a different office with the trailer and have it inspected. They inspect only the NCX number stampings. I didn't have a floor or tailights on it. This took 10 minutes of waiting and 30 seconds of signing the same paper from #1. No payment needed. The inspections only happen from 8am to 10am M-F or you can make an appt. and they will come to your house and do it - appts. are several months out.
4. Go back to the DMV and and pay your $$. I got plates, title, taxes done for $133 - this is for plates for the life of the trailer. Take $50 off of that number for annual plates. You need $5 of this in cash, the rest by check and proof of insurance for the tow vehicle.
Hope this helps. WooHoo - I'm legal!
Ryan