Go with the FRED. I would rather the coach have the old tires and use such to bargain the price down and then get tires I want and not the off market low cost brands the current owner may have installed to help make the sale.
Also as Triker33 shows it's not the price per gallon of fuel at the pump but the cost per mile. You only need a few miles to a gallon increase to make up for the cost difference fuel price.
Also for your budget planning keep a reserve of 10% beyond final sale price. Sometimes a used coach may need a bit of work or updates to get it to your personal standards of living and preventative maintenance routine. And a six hour drive to check the coach out is not unusual. I did it three times with my coach. Drove it home on the third trip.
(EDIT) Was wondering what the bunk bed layout would look like in the FRED model and looking at the model archeive on the Tiffin web site I couldn't find anything. No 35QBA in the Bay series and no bunk beds in any of the Bay series up to 2010 when the line was closed. Are you sure it's a FRED?
