257.721 Passenger vehicle or pickup truck towing vehicle or trailer; drawbar or other connection; coupling devices and safety chains; pickup truck with fifth wheel assembly; conditions for towing additional trailer or semitrailer; speed limit requirements; violation as civil infraction.
Found these specs
ReeseTitan Class V Receivers WD 14,000 GTW 1,700 GTW
Titan WD Hitch GTW 17,000 GTW 1,700
Reese 2 5/16" Ball 1 1/4" Shank 17,000 lbs Capacity
Bulldog flat mount 2 5/16 coupler 25,000 lbs capacity
As far a building the trailer yourself call and get some pricing on Axles and steel. Around here scrap prices have fell but new steel price is still high, running over a $1.00 pound here. There are a couple of salvage guys local here that get overruns, seconds, drops, etc. and they get $.70-.75 per pound for there stuff. These trailers usually have a 6" or 8" rail and matching cross members, and tongue also.
6" channel 8.2 lbs per foot
8" channel 11.5 lbs per foot
Hope this helps