I bought a 2 year old Cardinal back in 2003 and just traded it in on a 2015 Cedar Creek Silverback. Both are Forest River products. At the time of the trade the Cardinal was in excellent shape and we had very few problems over the 12 years we owned it. Have used our new Silverback for a month while still in Florida for the winter and love it.
Prior to trading our Cardinal I was looking for a nice used 5th wheel in the same years that you are now looking to buy. Expect to pay between $20K and up to $35K for something in that age range. We looked far and wide while at home in Michigan the past 2 years, but found that the choices were better in Florida. You'll feel it when you see it. A good used unit should be in well taken care of by the previous owners, otherwise I'd back off. It would be nice to find an owner with receipts for all previous repairs. That should show you how well it was taken care of.
2018 Chevy 2500HD Duramax - 2015 Cedar Creek Silverback 29RE
16K Huskey EZ Roller Hitch - EU2000i Honda Generator