If you can afford $19,500 you should be able to afford just a little bit more. I'd pay the extra for a new one with peace of mind and a warranty. Do you absolutely have to have a crew cab? If you go for a crew cab they are the most expensive. I'd go with a quad cab. They still have plenty of space in the back plus you get the bigger bed. $19,500 puts you into a $400 payment range with 60 month loan and mind you interest rates are higher on used vehicles.
If you could get into a new one for 24k (for example) with a 3.2% interest loan for 72 months you'd be looking at a payment of $366.80 a month. You might be able to get a quad cab for a bit cheaper new out the door. At least look into it, I urge you. With used you might be getting a gem that was well taken care of, or you could be getting a **** that someone drove into the ground. Don't forget the 09s are a first year production.