Thanks for all the comments, they were helpful and very very informative. This is the information I was looking for. Some of them confirmed my thoughts and others were new things to consider.
The skies cleared this afternoon and there was going to be some good weather before it starts raining again on Friday. So after checking the weather radar, I texted the seller asking if I could come back over and take a closer look at the rig since the skies were bright an sunny. I was there within an hour.
I was able to crawl under the rig with my small bright flashlight and check the transmission, back side of wheels, checked for any kind so leaks, etc. The seller showed up from his job about the same time I did. I was able to open both panels in front and spend more time looking at the front part of the engine, hoses, radiator and fluids.
I was also able to go back inside and take a closer look. I also asked him to explain to me where the tanks were, how to winterize if needed. I rechecked places I had checked before for any kind of signs of water stains.
I also asked some repeat questions and received different answers from Tuesday but a more clearer picture about the history of the rig.
What I need to know is, should it be a deal breaker that this rig has been parked and unused for 4 years, no trips, no short trips, not driven anywhere, not even to put gas in the tanks...or from new things I found in today's inspection??
What I found with my 2nd inspection that was more in depth due to the clear weather is as follows:
1. He used the floor jack that was sitting in front of the rig to raise the rig and change the front tires himself. Both were new Bridgestones.
2. He said he also changed the 6 rear tires with Michelins where the tread was ok but not new like the front tires. I noticed the side walls showed cracking as in old but couldn't find the 4 digits to tell me how old the tires were. There was enough sidewall cracking that I would install new tires before heading on a 8 month journey.
3. I asked him like I did Tuesday if he had the rig serviced at the local RV dealer/service. Today he said he never did, that he did all the servicing himself, Tuesday he said they had done some. When I called them on Wednesday to check, they knew him by name but had never worked on his RV.
4. The bottom black color all the way around was stained or delaminated with white stains but had never been driven in the winter on salty roads. I opened every bay, one thing I could not do during the rain storms. EVERY bin door on the back side was rotten. He suggested ways of repairing it, like drilling out the rivets and inserting new 3/4" wood. Still literally every bin door was water damaged on the inside. Each bin had looked like it had not been used in a long time, evidenced by dirt and a lot mice droppings and nests.
5. The generator looked clean, oil level was good and had a new filter but had only a few hours over 100. He said "I think it runs or it should run once there is enough gas in the tank but I ever used it. I always hooked up to campground power when I used it" Later I can explained but he used it the first 6 years of owning it for 10.
6. The large bin included the water hoses, power cord, a bag of something, a small grill. I would replace everything I saw with new units.
7. The awning and rails looked fairly new but he said they were changed out before he bought it from his dad.
8. After going inside he lifted one of the beds to show me the valves of the water system and how to winterize. That area and plumbing looked good as new. I checked again under all the windows to check for water stains, there were none.
9. Lifted the stove unit below the burners and found evidence of a lot of mice traffic.
Things I found today that I didn't see Tuesday did make me feel less confident in my previous decision. The interior was nice but wasn't as impressive as I has seen with the lights on. All the plumbing under the sinks look in good shape with no signs of water damage.
So I am asking the readers with experience, is what I found today enough to change my decision. Are there future problems lurking with the rig sitting for 4 years and never used. From the title he showed me, it is a 1987, he bought it in 2004 so he has owned it 10 years and used it the first 6 years of ownership.
The ground was too saturated today to back it out for a test drive. He also mentioned Sunday as a pickup day not Saturday as originally planned.
Thanks for your help. I will be by the computer most of the night to answer any questions by email or reply to comments.