Thank you all for the helpful replies. @ajriding - I didn't see your pics come through, but to your comment, I'm not very handy at doing the level of work you described - I could do it with some good YouTube videos, but frankly am not very motivated if the time/cost are beyond the value of the trailer itself.
If it comes through, attached are links to photos of it. One is of the tarped RV and the other is of the roof spot where the sagging is starting - the brown spots are all dirt, not mold or holes or anything. Last year I sealed the entire roof with a few coats of roof sealant and it did stop some leaks, but then it began pooling up a few months ago by the AC unit and then sagging more as of yesterday a little further out from the AC unit (you can see some circles where the water was sitting before I brushed it out).
Does any of this additional insight change anyone's opinion about how salvageable it is or perhaps how I can prevent more rain from collecting?