Like others have said, it depends on what you want to do. I did a job much worse than this last year for my neighbor.
The roof was really, really bad. I told them what do you want to do because the trailer is totalled. They had an emotional attachment to the trailer because it was their parents trailer.
I told them look, I can stop the leaks but the roof is junk and so are most of the side walls. They said they just wanted me to stop the leaks so it does not get water inside. I gave them a bid and they said yes.
I first put eternabond on all the perimeter of the roof. Then I put
this on the whole roof.The trailer does not leak anymore, but the inside of the trailer is kind of a mess but they were very happy with the job I gave them.
If you do this, your trailer will not leak.