Jonlin, you are considering one of the most popular motorhomes on the market.
Six batteries will run your fridge for most of a day but that will depend on the use of other items. Generally, it is recommended to run the generator 2 hrs. in the morning and 2 hrs. in the evening if you are boondocking.
If this coach is on the original batteries, they might be at the end of their life. If you do need to replace the batteries, consider AGM's, they are cleaner and you don't have to worry so much about sulfating and watering the batteries. That a big pain in the hiney.
Check tire date codes too.
Good luck, those are popular motorhomes.
MM.