2005 Z71 1/2 ton Suburban

My wife and I are new to the rving scene and we have decided to go Airstream from the start. The new ones are a bit pricey and seeing as how we are new to this, we are looking at previously enjoyed models. My question is this: I have a 2005 Z71 1/2 ton Chevy Suburban. I understand that I have a towing capacity of around 7200#. I was looking at new models in the empty weight area of 5 to 6 thousand pounds. As I am looking at the older models, how do I know what the older ones weigh? Is there a chart I can reference? I see some photos on here of people towing 30 footers with smaller vehicles. We don't need a huge trailer, 25-28 is plenty. Any info from my new friends here on the forums would be greatly appreciated.