Not sure about other states but Michigan has uped the length of pulling recreational doubles from 65' to 75'. I built a trailer to haul my Toyota behind my 5th wheel that being said. Any trailer with a 3500 lb gross needs to have brakes on all axles (I have electric on 5th wheel and surge brakes on yota trailer) also the rear trailer can not weigh more then the tow rig but must weigh less then the 5th wheel. You are also going to want to run some sort of weight distribution hitch between the 5th wheel and the back trailer. I had an issue with pulling both because once the yota was loaded the tounge weight of said trailer pulled weight out of the back of my truck witch caused the 2 trailer to sway way more then I liked.
Here is a pic of my set up hope this info might be of some help.
Always missed, Never forgotten
08' 4door JK 5.7 hemi, auto, atlas and tons
2012 F350 6.7 PSD CC shortbox