Covid changed a few things. The DMV's near me stopped doing inspections because of it. I hope they start back up soon. As for regulations, most are based on weight.
Here is one of the links.
CA DMV
You need to research "SPCNS" I found an area on trailers before but don't have time right now to find the specific info.
I may be off on the numbers but, 1500# it needs brakes, 2000# they want a weight slip and 2500# it needs the switch that applies the trailer brake if it comes off the hitch.
The last one I did a few years ago, I made an appointment, the lady came out, made sure the lights worked, saw it had brakes, asked how much it cost (told her 300) and gave me a VIN tag.
What I read recently said they wanted receipts for the build to value it and if it looked heavy, a weight slip.