class c repair

Are you certain there is a leak or could it be that it is just condensation from lack of air flow under that mattress? The bottom of my bunk mattress is vinyl and if I let it sit directly on the overhead platform, it will sweat.
I installed a mesh material used for underlayment under metal roofs that allows air to circulate under the mattress and now all is well.

I agree with ed6713; if you have basic carpentry skills patients and some desire you can repair it. If not walk away from it. There is a lot of folks on here and other sites such as goodoldrvs that have info on this subject and offer advice and encouragement. If you don't go walking go surfing and good luck on what ever you decide.

IF you have the necessary skills, equipment, money, time and facility, finding then repairing an unknown amount of water damage, possible delamination, etc. is doable.

Otherwise, I would keep searching rather than buying someone's problems.