Sorry to her about your leak situation. Water damage is one of the worst things that can happen to a camper. The water intrusion often goes un-noticed until the damage from rot has advanced to the stages you can see signs of it. Just how far the damage is, is one of those real unknowns. It may be a small area or very involved and most times it is not known until the camper is opened up to inspect.
There is some level of good news in all this, these campers are totally rebuildable/fixable. With basic wood working tools, skills and some help on how these things where built, all is fixable.
Now comes the other part of this. Money $$$ To hire this out at standard RV dealership costs can become very quickly cost prohibitive for an older camper. With shops rates ranging from $65 to $100 an hour , 2 technicians cost between $1,000 to $2,000 a day plus materials pending rate.
If the owner can do the labor themselves, this becomes a labor of love and the materials cost is not that bad and fairly affordable. It seems you may not have a shop or the tools to be able to do all of this yourself. That said, do you have a family member or a good friend who can help at the right price? Pending who, food works wonders for compensation... I have done many a house, car, lawn mower etc. repair for a good dinner or apple pie
and never had a second thought it.
Now to the camper so you have a small level of what you are up against.
Weak areas of a camper are the corner seams, the roof seams, the window or door seams. Basically any seam exposed to weather, just some are worse than others. Some of this is due to the sealants used originally (putty tape) others is poor RV design.
From this basic description
When I went to put the canopy out where the bottom of the support poles screw in the bottom of the trailer sides, They just pulled out because of rotted wood. The door stop to hold the door open is also in rotted wood.So minimally the bottom side wood is rotted. When I looked at it I did know there had been a leak in the front corner above the seat to the table. As the wood there was very soft.I Was told it no longer leaked there, but it does.I think its possibly its just from the lack of the rubber gasket strip that goes down the corner.( The other corner has the gasket in it )
Here are some maybe's to the extend/cause. Really will not know until the camper is opened up to inspect.
Since the awning and the door stop area are rotted, this points to the lower sill plate of the wall is rotted. This lower area usually comes from water intrusion from above. How far above is a good question. If it started at the roof line due to the gutter rail water intrusion, the top frame plate up by the roof can have a level of rot and as the water continued down the wall where ever it stops and pools the rot starts. The bottom of the wall is the point it stops, sits, festers and then 1 to 2 years later there is not much left.
If the water entry came from a door or window flange seal, same thing can occurs just the door or window frame can be going or gone and the wall sill plate.
The camper corners are another bad actor. The corner joints have putty tape on them to help seal out the water. Over time the putty tape drys,out cracks and splits. If the camper is exposed to heavy rain, the water beating down on the side of the camper or off the roof beats into the 4 corners of the camper. The water finds that split in the sealant and soon starts wicking in side the camper. Once it gets in it cannot get out so it goes down until it stops. The insulation gets water soaked, can't dry out and the corner wood and the floor sill plate again rot out.
If the prior owner had a leak and they said it no longer leaks, they may be truthful for what they knew about campers. They may have caulked one source of the water entry and for the rain conditions at the time, the leak stopped. However if they never took the camper apart and fixed the wet soaked insulation and wood, then time is the enemy. It takes time for wood to rot to the point of total destruction. 2 to 3 months maybe even 6 to 8 months you may be able to recover from easier if you take the camper apart and fix it. If a year or 2 go by, the wood rot is really advanced. What ever patch the prior owner did was short term and over time another one in a different area started, the patch open up again and more water keeps coming in.
I'm not trying to paint the picture of gloom and doom, but the reality of what you may be up against so you can make a better decision on what to do next.
Here are some links of prior owners rot and repair.
Here is one of mine. While this is a slide floor rot issue, you can see what is involved in taking the camper apart, the corner seals, the rot and how to help check some areas before opening up the camper
This one is Frank's. He had water intrusion from the roof to wall seams and the water ended up down at the floor sill plate
Here is EMD's latest floor joist rebuild
And here are many more. This is the FAQ section in the "How To" sticky. Scroll down to the topic
Restoring a Sunline
1. Repairing water damage on your Sunline.
There are many links in there with lots of pics of camper rot.
Here is one way to attempt to get a level of how bad this "might" be. You yourself may be able to do this.
Do an inspection on the outside screws of the camper, the corners, the window and the door for starters.
Since you know the awning lower mount and the door holder are infected, you know the bottom sill plate board has issues. Now, how far up do we have the problem?
Try the front corner on that side. There should be a vinyl cover that snaps in to the corner strip. Look simailr to this. This is my roof gutter, but the corners are similar. Your older camper may be slightly different but there is still something that cover the screws
The rust screws heads is the beginning. I was lucky I found this before the advance of rusted screws created a water entry path. Take the screws out one at a time, inspect and put back in and tightened it.
This one is just the head is bad. The wood area is good. No rot inside
These are early stages of moisture. Wood is still not infected but the breakdown process has started. A few more years and this will be a real problem. Find an ice pic that the rod is small enough to fit in the hole. Probe it and see if the end of the hole is hard or spongy.
This level of rust from consecutive screws shows wood has been wet, the wood still holds a screw and is not yet heavily infected but there is a problem brewing. These where from my slide floor sill plate.
If you find this, the wood is gone. This was out of my slide floor.
When you put the screw back in a questionable area, if it will tighten up then you know the rot is not totally advanced at that location. If it slips non stop and will not bite to stop, the wood is infected and shot. You can ice pic probe in the hole too. If the wood is rock hard, you know that area is still good. If the pic starts working it's way in, there is a level of infection. In the corner section, start at the bottom and work your way up. You can tell where the corner is gone and where the rot stops.
Do the same around the door or window
The next is how to spot the leak from the inside. If you can see it inside, then the rot is advanced in that area. This video, while a sales job to sales extent by the dealer, he is talking good info in how to look.
Use your nose. Wood rot smells musty, mildew, wet. It is a smell once you learn and see the damage from it you will never forget that scent. Dry wood smells different. You may need to get your nose up close.
There is also a moisture meter. Jim (Jim44644) here on the forum has experience in using these. I have not, just learned the new trick from him. Probing the wall inside may help show what is suspect and what is not. He reads the forum often and I'm sure he can jump in here on where to buy/use them. He has posted on them in the past.
If you can get a general assessment on how good or bad you are, it will help what to do. You are going to have to sort out,
1. Can I find a helper to help with this? A small area may take 2 to 3 weekends, a large area may take a lot more.
2. If the damage is heavy, then do you consider selling the one you have and finding another one? If you go hunting for an another one, come back and let us help on what to look for. I'm sure after this inspection and undertaking you will know what to look for.
Hope this helps and good luck