The price is always negotiable. If it isn't, the price should be zero! In other words, walk away.
There is no such thing as a small exhaust leak on anything!
Plan on new tires. On a travel trailer that sits much of the year, plan on replacing them every 3-4 years or every 15K at most. Whichever comes first! I would expect the same for motorhomes. Inactivity lets the plasticizers evaporate-this is dry rot and UV degredation; use brings them to the surface to replenish them from the inside out. This is why auto tires last longer.
All appliances are probably original. They will all start to go soon. Figure the purchase price will be the down payment. Price of a new Dometic fridge $1,100-1,500. Depending on model and whether you install it or if RV shop installs. If you aren't handy and don't know your way around an RV, let the RV shop install it. You'll be glad you did. New A/C, $500-$700 installed. Again, same advice. New furnace, not sure about price but don't take any chances with anything that produces carbon monoxide like furnaces and exhaust systems. Hot water heater, same as furnace. Plumbing, probably leaks somewhere or has in the past and that spells floor rot. This can spell big bucks to remove the interior furnishings to get to those floor boards under the cabinets, especially those under the water heater and fridge. Window leaks and most "roof" leaks occur on outside walls. Again, those result in floor rot if they go undetected for any length of time, like during storage, and that is usually found under cabinets, behind furnature or other hard to get to places. Condensation during winter months will also occur on perimeter walls and find its way to the perimeter of the floor.
Engine will need some repairs unless it is a diesel. They last forever, but they really need more exercise than this one has had...by the way, how do you know that is original mileage. IIRC, the speedometers back then weren't always sealed against tampering. I believe that started around mid-'80's. Might not have been the dealer, might have been previous owner once or twice removed. Early '80's speedometers could be rolled back with a coat hanger.
Long and short of it is this is a 24 year old motor home. It is going to be a money pit either now or in the very near future. Make an informed decision and proceed cautiously.