The Tiffin Open Road (FRED) coach was a nice set up but never really caught on. Tiffin dropped the model when they started their Red line of rear engine diesels around 2010 or so. The house side was pretty much the same as their gas powered models they offered but the diesel power train had a higher initial cost. The gain of the front diesel over gas is better fuel mileage and enough of an increase to make up for the fuel cost difference with gasoline. Towing was still limited to 5K Lbs. Great engine/transmission set up that will easily outlive the house side but the rest of the chassis was nearly identical with the gas chassis available at the time so the overall gain wasn't enough for most potential buyers to get past the initial increased cost.
If the coach you're looking at is priced right for the general sub-class and a test drive is satisfactory concerning performance and such associated with a front engine no real reason to walk away.