I agree with all of the above..... If you have no experience rebuilding trailers it will not be worth while and will more than likely end up being an unfinished project with a lot of time and money put into it. Paying someone else to do the work is going to be really expensive..
It would be much cheaper to buy one in good used condition.
There is lots of good info on the net, as well as YouTube videos of others who have completely rebuilt trailers. Do your research first before making your decision...
And why would you possibly need 50 amp service????
Good luck in whatever you choose.