"Overall the trailer seems in good shape but for this leak the previous owner had."
Leaks are probably the worst problem a trailer/mh can have, along with the health problems generated by mold. The cost to do enough of a teardown to completely track and eliminate the water/mold damage, which can affect a broad area, then restore to original, can be overwhelming in what has to be done and the cost to do it.
I believe few owners will willingly hold onto an RV/trailer once a leak has sprung if they can get out of it financially.
Most fixes I have seen as an inspector are mostly trying to stop a leak coming in, but often leaving the cosmetic giveaways untouched. The owner ignored the underlying need to do a teardown to determine the actual extent of the damage internally.
If you can name a worse problem, let me know.