I purchased a 2006 on a E450 chassis recently. Paid under 30K for it. Drives and handles fine. There are thousands of pre 2008 E's on the road. I would not worry about it, just watch your weight which you should do anyway. Only thing I was looking for was the E450 and not E350 as I wanted the wider wheelbase.
If you look carefully you should be able to find a clean low mileage mid size C built in the mid 2000s for under 30K. I kept watching for a month and found one. You will have to look and be ready to purchase quickly when you fine one. Getting close to the beginning of the season though so prices will be inching back up. Middle of winter is a good time to buy.
