I'm not bashing you or the hubby but if you have to ask how to start tells me you shouldn't mainly because you have no place to keep the exposed unit out of the elements (rain/wind/etc). This isn't a job that can be done in a couple of weeks with a hammer and a power saw.
If the roof is rotted the metal has to come off first....then attention to the side/front and rear walls and possibly the floor if it needs to be replaced.
When removing the metal from the ground up match mark each piece where it meets the next one. I always started with a A1...A2 ...A3/etc for one side and used a B1....B2/ for another and so on around the trailer.
Tarps ??
If you use those blue thin Walmart then plan on replacing them often. I would invest in a heavier canvas type.
Good luck
